diff --git a/docs/content/docs/api/reference/contacts.mdx b/docs/content/docs/api/reference/contacts.mdx
index 346c6d1c2..493c14a41 100644
--- a/docs/content/docs/api/reference/contacts.mdx
+++ b/docs/content/docs/api/reference/contacts.mdx
@@ -33,7 +33,7 @@ Every field is optional; an empty body matches all contacts in the organization.
 | `category_ids` | string[] | No | Contact must have ALL of these categories. |
 | `segment_ids` | string[] | No | Contact must be a member of ALL of these segments (conditions plus manual overrides). An id that is not a valid UUID is rejected with `400`; an unknown segment matches nothing. |
 | `verification_status` | string | No | Filter by verification verdict: `valid`, `risky`, `invalid`, or `unknown`. |
-| `mail_hosts` | string[] | No | Contacts whose inbox is hosted by any of these `mail_host` values (see [Email provider](#email-provider)). `""` matches contacts whose provider is not detected yet. An unknown value is rejected with `invalid_mail_host`. |
+| `mail_hosts` | string[] | No | Contacts whose inbox is hosted by any of these `mail_host` values (see [Email provider](#email-provider)). `""` matches contacts with no known provider: not checked yet, or a domain with no mail server. An unknown value is rejected with `invalid_mail_host`. |
 | `min_campaigns` | integer | No | Minimum number of associated campaigns. |
 | `max_campaigns` | integer | No | Maximum number of associated campaigns. |
 | `subscribed` | boolean | No | Filter by subscription status. |
@@ -41,7 +41,7 @@ Every field is optional; an empty body matches all contacts in the organization.
 | `created_before` | string (RFC 3339) | No | Created on or before this time. |
 | `updated_after` | string (RFC 3339) | No | Updated on or after this time. |
 | `updated_before` | string (RFC 3339) | No | Updated on or before this time. |
-| `sort_by` | string | No | Sort column: `created_at` (the default), `updated_at`, `first_name`, `last_name`, `email`, `company`, `phone`, `campaign_count`, or `mail_host`. `mail_host` sorts by the provider value, with contacts whose provider is not detected yet grouped last when ascending and first when descending. `custom:<key>` sorts on a custom field, as text, with contacts that lack the field (or have it blank) grouped last when ascending and first when descending. A custom-field name that could never exist is rejected with `invalid_sort_by`; any other unknown value falls back to `created_at`. |
+| `sort_by` | string | No | Sort column: `created_at` (the default), `updated_at`, `first_name`, `last_name`, `email`, `company`, `phone`, `campaign_count`, or `mail_host`. `mail_host` sorts by the provider value, with contacts that have no known provider grouped last when ascending and first when descending. `custom:<key>` sorts on a custom field, as text, with contacts that lack the field (or have it blank) grouped last when ascending and first when descending. A custom-field name that could never exist is rejected with `invalid_sort_by`; any other unknown value falls back to `created_at`. |
 | `reverse` | boolean | No | Ascending when true. The default is descending. |
 
 ```json
@@ -104,7 +104,7 @@ Every contact carries `mail_host`, who hosts the inbox the address belongs to, a
 
 When the search filters by exactly one campaign, each contact additionally carries a `campaign_lead` object with its processing state inside that campaign (`status`, `sent`, `opened`, `machine_opened`, `clicked`, `replied`, `bounced`, `current_step`, `sender`, `last_activity_at`, `hold` when held, and `failure_reason` when failed). `sender` is the mailbox address the lead's whole sequence sends from, fixed when its first email went out and absent until then. `opened` counts steps opened by a person; steps fetched automatically by a mail client (Apple Mail Privacy Protection and similar) are in `machine_opened` instead, matching the machine opens the analytics summary reports. The `status` derivation, highest priority first, is `unsubscribed` (not subscribed), then `bounced`, `replied`, `failed` (a step could not be sent after every retry; `failure_reason` carries the sending worker's reason), `completed` (every email step sent, no reply), `paused` (the lead's flow is held, by an out-of-office auto-reply or by hand; the `hold` object carries `since`, `until`, `reason` and `source`), `active` (some steps sent, more to send), `undeliverable` (pre-send verification refused the address, so the campaign skips the lead and never sends to it), and `pending` (queued, nothing sent). A step counts as sent only once the sending worker has delivered it to the mailbox provider; a send the worker could not complete is retried on the campaign's next pass and never shows as sent. The `lead_status` filter narrows to one of these buckets.
 
-When the search filters by exactly one campaign, the first page (no `cursor`) also includes a `lead_counts` object: per-status lead totals for that campaign, independent of the `lead_status` and `engagement` filters so every scope's total is available at once. The status buckets include `paused`. Alongside them it carries engagement totals that match the `engagement` filter: `contacted` (leads sent at least one step), `opened` (a human open on any step), `clicked`, and `replied_any` (a reply on any step, whatever the derived status). `providers` splits the campaign's leads by [email provider](#email-provider) family, the grouping ESP matching uses: `gmail`, `outlook`, `other`, and `undetected` for leads whose provider has not been read yet.
+When the search filters by exactly one campaign, the first page (no `cursor`) also includes a `lead_counts` object: per-status lead totals for that campaign, independent of the `lead_status` and `engagement` filters so every scope's total is available at once. The status buckets include `paused`. Alongside them it carries engagement totals that match the `engagement` filter: `contacted` (leads sent at least one step), `opened` (a human open on any step), `clicked`, and `replied_any` (a reply on any step, whatever the derived status). `providers` splits the campaign's leads by [email provider](#email-provider) family, the grouping ESP matching uses: `gmail`, `outlook`, `other` (including checked domains with no known provider, which ESP matching treats the same way), and `undetected` for leads whose provider has not been read yet.
 
 ```json
 {
diff --git a/docs/content/docs/guides/contacts-crm.mdx b/docs/content/docs/guides/contacts-crm.mdx
index 721e3bf50..101286f7b 100644
--- a/docs/content/docs/guides/contacts-crm.mdx
+++ b/docs/content/docs/guides/contacts-crm.mdx
@@ -109,7 +109,7 @@ A sort on a custom field orders the values as text. Contacts that do not have th
 
 The **Email provider** column shows who hosts each contact's inbox: Google Workspace, Gmail, Microsoft 365, Outlook.com, Yahoo Mail, iCloud Mail, Zoho Mail and the other hosts Warmbly recognises, with the provider's logo. It works for company domains too: `dana@acme.com` reads as Google Workspace when Acme's mail is hosted by Google. Warmbly reads it from the domain's mail records in the background, usually within a minute of a contact being added, and fills the list in live. A dash means the check has not reached the contact yet, or the domain has no mail server at all.
 
-It is part of the standard layout on the contacts page (if you have already arranged your own columns, add it from **Columns**) and one tick away in the column chooser on a campaign's Leads tab. From there you can sort by it, filter with **Add filter** > **Email provider** (including **Not detected yet**), select every match and act on them in bulk (add them to a campaign, tag them, export them), or save the filter as a segment. Campaign [ESP matching](/guides/campaigns/) uses the same data to pair each lead with a same-provider mailbox.
+It is part of the standard layout on the contacts page (if you have already arranged your own columns, add it from **Columns**) and one tick away in the column chooser on a campaign's Leads tab. From there you can sort by it, filter with **Add filter** > **Email provider** (including **Unknown or not checked yet**), select every match and act on them in bulk (add them to a campaign, tag them, export them), or save the filter as a segment. Campaign [ESP matching](/guides/campaigns/) uses the same data to pair each lead with a same-provider mailbox.
 
 ## Selecting rows
 
diff --git a/docs/public/openapi.json b/docs/public/openapi.json
index 404c5afbf..a52430c98 100644
--- a/docs/public/openapi.json
+++ b/docs/public/openapi.json
@@ -29613,7 +29613,7 @@
             "items": {
               "type": "string"
             },
-            "description": "Contacts whose mail_host is any of these; \"\" matches contacts whose provider is not detected yet. An unknown value is rejected with 400 invalid_mail_host."
+            "description": "Contacts whose mail_host is any of these; \"\" matches contacts with no known provider (not checked yet, or a domain with no mail server). An unknown value is rejected with 400 invalid_mail_host."
           },
           "subscribed": {
             "type": "boolean"
@@ -29636,7 +29636,7 @@
           },
           "sort_by": {
             "type": "string",
-            "description": "Sort column: created_at (the default), updated_at, first_name, last_name, email, company, phone, campaign_count, or mail_host (contacts whose provider is not detected yet grouped last when ascending and first when descending). custom:<key> sorts on a custom field as text, with contacts lacking the field grouped last when ascending and first when descending; a custom-field name that could never exist is rejected with 400 invalid_sort_by. Any other unknown value falls back to created_at."
+            "description": "Sort column: created_at (the default), updated_at, first_name, last_name, email, company, phone, campaign_count, or mail_host (contacts with no known provider grouped last when ascending and first when descending). custom:<key> sorts on a custom field as text, with contacts lacking the field grouped last when ascending and first when descending; a custom-field name that could never exist is rejected with 400 invalid_sort_by. Any other unknown value falls back to created_at."
           },
           "reverse": {
             "type": "boolean",
diff --git a/internal/jobs/contact_mail_host.go b/internal/jobs/contact_mail_host.go
index 8d9875d14..e67294306 100644
--- a/internal/jobs/contact_mail_host.go
+++ b/internal/jobs/contact_mail_host.go
@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"github.com/redis/go-redis/v9"
 	"github.com/rs/zerolog/log"
 
 	"github.com/warmbly/warmbly/internal/config"
@@ -20,8 +21,14 @@ const (
 	contactMailHostMaxPasses = 50
 	contactMailHostLease     = "lock:contactmailhost"
 	contactMailHostLeaseTTL  = 10 * time.Minute
+	// contactMailHostRunBudget ends a run while the lease still has room for
+	// the lookups already in flight, so two replicas never sweep at once.
+	contactMailHostRunBudget = contactMailHostLeaseTTL - 2*time.Minute
 )
 
+// releaseContactMailHostLease deletes the lease only while this run still holds it.
+var releaseContactMailHostLease = redis.NewScript(`if redis.call("GET", KEYS[1]) == ARGV[1] then return redis.call("DEL", KEYS[1]) end return 0`)
+
 // ContactMailHostStore is the slice of the contact repository the sweep uses.
 type ContactMailHostStore interface {
 	ListMailHostPending(ctx context.Context, limit int) ([]repository.ContactMailHostPending, error)
@@ -55,13 +62,15 @@ type cachedMailHost struct {
 func (j *ContactMailHostSweep) Run(ctx context.Context) error {
 	// One replica sweeps at a time; a Redis outage fails open.
 	if j.cache != nil {
-		if got, err := j.cache.SetNX(ctx, contactMailHostLease, "1", contactMailHostLeaseTTL).Result(); err == nil {
+		token := uuid.NewString()
+		if got, err := j.cache.SetNX(ctx, contactMailHostLease, token, contactMailHostLeaseTTL).Result(); err == nil {
 			if !got {
 				return nil
 			}
-			defer j.cache.Del(context.WithoutCancel(ctx), contactMailHostLease)
+			defer releaseContactMailHostLease.Run(context.WithoutCancel(ctx), j.cache, []string{contactMailHostLease}, token)
 		}
 	}
+	deadline := time.Now().Add(contactMailHostRunBudget)
 	for range contactMailHostMaxPasses {
 		pending, err := j.contacts.ListMailHostPending(ctx, config.ContactMailHostBatchSize)
 		if err != nil {
@@ -70,10 +79,14 @@ func (j *ContactMailHostSweep) Run(ctx context.Context) error {
 		if len(pending) == 0 {
 			return nil
 		}
-		hosts := j.resolveDomains(ctx, pending)
+		hosts, skipped := j.resolveDomains(ctx, pending, deadline)
 		results := make([]repository.ContactMailHostResult, 0, len(pending))
 		for _, p := range pending {
-			r, ok := hosts[mailhost.NormalizeDomain(p.Email)]
+			d := mailhost.NormalizeDomain(p.Email)
+			if skipped[d] {
+				continue
+			}
+			r, ok := hosts[d]
 			res := repository.ContactMailHostResult{ID: p.ID, Email: p.Email, Transient: !ok}
 			if ok {
 				res.MailHost, res.ESP = string(r), mailhost.ESPFamily(r)
@@ -89,7 +102,7 @@ func (j *ContactMailHostSweep) Run(ctx context.Context) error {
 				j.reloader.PublishOrgContactsReload(ctx, org.String(), "contacts:mail_host")
 			}
 		}
-		if len(pending) < config.ContactMailHostBatchSize || ctx.Err() != nil {
+		if len(pending) < config.ContactMailHostBatchSize || len(skipped) > 0 || ctx.Err() != nil {
 			return ctx.Err()
 		}
 	}
@@ -97,9 +110,10 @@ func (j *ContactMailHostSweep) Run(ctx context.Context) error {
 }
 
 // resolveDomains answers each distinct domain once. A domain missing from the
-// result failed transiently.
-func (j *ContactMailHostSweep) resolveDomains(ctx context.Context, pending []repository.ContactMailHostPending) map[string]mailhost.Host {
+// result failed transiently; one in skipped was not asked before the deadline.
+func (j *ContactMailHostSweep) resolveDomains(ctx context.Context, pending []repository.ContactMailHostPending, deadline time.Time) (map[string]mailhost.Host, map[string]bool) {
 	out := map[string]mailhost.Host{}
+	skipped := map[string]bool{}
 	var todo []string
 	for _, p := range pending {
 		d := mailhost.NormalizeDomain(p.Email)
@@ -110,6 +124,10 @@ func (j *ContactMailHostSweep) resolveDomains(ctx context.Context, pending []rep
 		if d == "" {
 			continue
 		}
+		if h := mailhost.KnownDomain(d); h != mailhost.Unknown {
+			out[d] = h
+			continue
+		}
 		var hit cachedMailHost
 		if j.cache != nil && j.cache.GetJSON(ctx, contactMailHostKey(d), &hit) == nil {
 			out[d] = mailhost.Host(hit.Host)
@@ -122,8 +140,13 @@ func (j *ContactMailHostSweep) resolveDomains(ctx context.Context, pending []rep
 	var wg sync.WaitGroup
 	sem := make(chan struct{}, config.ContactMailHostConcurrency)
 	for _, d := range todo {
-		wg.Add(1)
 		sem <- struct{}{}
+		if time.Now().After(deadline) {
+			<-sem
+			skipped[d] = true
+			continue
+		}
+		wg.Add(1)
 		go func(d string) {
 			defer wg.Done()
 			defer func() { <-sem }()
@@ -144,7 +167,10 @@ func (j *ContactMailHostSweep) resolveDomains(ctx context.Context, pending []rep
 		}(d)
 	}
 	wg.Wait()
-	return out
+	for d := range skipped {
+		delete(out, d)
+	}
+	return out, skipped
 }
 
 func contactMailHostKey(domain string) string { return "contactmailhost:" + domain }
diff --git a/internal/jobs/contact_mail_host_test.go b/internal/jobs/contact_mail_host_test.go
index fb89d5183..40b7c07ea 100644
--- a/internal/jobs/contact_mail_host_test.go
+++ b/internal/jobs/contact_mail_host_test.go
@@ -5,6 +5,7 @@ import (
 	"net"
 	"sync"
 	"testing"
+	"time"
 
 	"github.com/google/uuid"
 
@@ -95,3 +96,23 @@ func TestContactMailHostSweep(t *testing.T) {
 		t.Errorf("a consumer domain dialled DNS")
 	}
 }
+
+func TestContactMailHostSweepSkipsPastDeadline(t *testing.T) {
+	dns := &mailHostDNS{mx: map[string][]string{"acme.example": {"aspmx.l.google.com"}}, calls: map[string]int{}}
+	j := NewContactMailHostSweep(&mailHostStore{}, nil, nil)
+	j.resolver = dns
+	pending := []repository.ContactMailHostPending{
+		{ID: uuid.New(), Email: "a@acme.example"},
+		{ID: uuid.New(), Email: "dana@gmail.com"},
+	}
+	hosts, skipped := j.resolveDomains(context.Background(), pending, time.Now().Add(-time.Second))
+	if !skipped["acme.example"] || dns.calls["acme.example"] != 0 {
+		t.Fatalf("a lookup past the deadline ran: skipped=%v calls=%v", skipped, dns.calls)
+	}
+	if _, ok := hosts["acme.example"]; ok {
+		t.Fatal("a skipped domain has an answer")
+	}
+	if hosts["gmail.com"] != "gmail" {
+		t.Fatalf("a known domain needs no lookup and is never skipped: %v", hosts)
+	}
+}
diff --git a/internal/models/contact.go b/internal/models/contact.go
index 92893fc07..0fb7d54f4 100644
--- a/internal/models/contact.go
+++ b/internal/models/contact.go
@@ -241,7 +241,8 @@ type CampaignLeadCounts struct {
 	Providers CampaignLeadProviderCounts `json:"providers"`
 }
 
-// CampaignLeadProviderCounts are a campaign's leads by esp_provider family;
+// CampaignLeadProviderCounts are a campaign's leads by esp_provider family.
+// Other includes checked domains with no known host, which match like other;
 // Undetected counts the leads the provider check has not reached yet.
 type CampaignLeadProviderCounts struct {
 	Google     int `json:"gmail"`
diff --git a/internal/pkg/mailhost/recipient.go b/internal/pkg/mailhost/recipient.go
index 14ca80a94..87a7b1256 100644
--- a/internal/pkg/mailhost/recipient.go
+++ b/internal/pkg/mailhost/recipient.go
@@ -24,7 +24,7 @@ func Recipient(ctx context.Context, r RecipientResolver, domain string) (Host, b
 	if norm == "" {
 		return Unknown, true
 	}
-	if h, _, ok := known(norm); ok {
+	if h := recipientKnown(norm); h != Unknown {
 		return h, true
 	}
 	if r == nil {
@@ -53,8 +53,19 @@ func Recipient(ctx context.Context, r RecipientResolver, domain string) (Host, b
 // KnownDomain names the host of a consumer mail domain, or of an address's
 // domain, from the built-in list with no DNS; Unknown for anything else.
 func KnownDomain(s string) Host {
-	h, _ := knownDomain(NormalizeDomain(s))
-	return h
+	return recipientKnown(NormalizeDomain(s))
+}
+
+// recipientKnown is knownDomain plus Microsoft 365 tenant domains, which are
+// Microsoft's mail but not a consumer service, so SharedProvider leaves them out.
+func recipientKnown(domain string) Host {
+	if h, ok := knownDomain(domain); ok {
+		return h
+	}
+	if strings.HasSuffix(domain, ".onmicrosoft.com") {
+		return Microsoft365
+	}
+	return Unknown
 }
 
 // ESPFamily is h's family as campaign ESP matching and contacts.esp_provider
diff --git a/internal/pkg/mailhost/recipient_test.go b/internal/pkg/mailhost/recipient_test.go
index c8544c215..b9f28225d 100644
--- a/internal/pkg/mailhost/recipient_test.go
+++ b/internal/pkg/mailhost/recipient_test.go
@@ -48,6 +48,7 @@ func TestRecipient(t *testing.T) {
 		{"gmail.com", Gmail, true},
 		{"hotmail.co.uk", Outlook, true},
 		{"icloud.com", ICloud, true},
+		{"contoso.onmicrosoft.com", Microsoft365, true},
 		{"yahoo.com", Yahoo, true},
 		{"acme.example", GoogleWorkspace, true},
 		{"contoso.example", Microsoft365, true},
@@ -76,3 +77,12 @@ func TestRecipientKnownDomainSkipsDNS(t *testing.T) {
 		t.Fatalf("known domain dialled DNS %d times", f.mxCalls)
 	}
 }
+
+func TestKnownDomainTenant(t *testing.T) {
+	if got := KnownDomain("ops@contoso.onmicrosoft.com"); got != Microsoft365 {
+		t.Fatalf("tenant domain = %q", got)
+	}
+	if SharedProvider("contoso.onmicrosoft.com") {
+		t.Fatal("a tenant domain is not a consumer provider")
+	}
+}
diff --git a/internal/repository/contact_mail_host_live_test.go b/internal/repository/contact_mail_host_live_test.go
index fbadc8a05..84ec9fa13 100644
--- a/internal/repository/contact_mail_host_live_test.go
+++ b/internal/repository/contact_mail_host_live_test.go
@@ -124,8 +124,9 @@ func TestLiveContactMailHostSweepWritesAndSearchReads(t *testing.T) {
 	if xerr != nil {
 		t.Fatalf("lead counts: %v", xerr)
 	}
-	if p := counts.Providers; p.Google != 1 || p.Microsoft != 0 || p.Other != 0 || p.Undetected != 3 {
-		t.Fatalf("lead counts by provider = %+v, want 1 Google and 3 undetected", p)
+	// The failed lookup was checked, so it counts with other; two were never reached.
+	if p := counts.Providers; p.Google != 1 || p.Microsoft != 0 || p.Other != 1 || p.Undetected != 2 {
+		t.Fatalf("lead counts by provider = %+v, want 1 Google, 1 other and 2 undetected", p)
 	}
 
 	for _, reverse := range []bool{true, false} {
diff --git a/internal/repository/pg_contact.go b/internal/repository/pg_contact.go
index bdfc7efb0..715591843 100644
--- a/internal/repository/pg_contact.go
+++ b/internal/repository/pg_contact.go
@@ -2185,8 +2185,8 @@ func (r *contactRepository) CampaignLeadCounts(ctx context.Context, orgID, campa
 			COUNT(*) FILTER (WHERE COALESCE(pr.has_replied, false)) AS replied_any,
 			COUNT(*) FILTER (WHERE c.esp_provider = 'gmail') AS provider_gmail,
 			COUNT(*) FILTER (WHERE c.esp_provider = 'outlook') AS provider_outlook,
-			COUNT(*) FILTER (WHERE c.esp_provider = 'other') AS provider_other,
-			COUNT(*) FILTER (WHERE c.esp_provider = '') AS provider_undetected
+			COUNT(*) FILTER (WHERE c.esp_provider = 'other' OR (c.esp_provider = '' AND c.esp_resolved_at IS NOT NULL)) AS provider_other,
+			COUNT(*) FILTER (WHERE c.esp_provider = '' AND c.esp_resolved_at IS NULL) AS provider_undetected
 		FROM campaign_leads cl
 		JOIN contacts c ON c.id = cl.contact_id AND c.organization_id = $2
 		CROSS JOIN (SELECT COUNT(*) AS total_steps FROM sequences st WHERE st.campaign_id = $1 AND st.kind = 'email') ts
diff --git a/web/src/components/app/contacts/filters/FilterBar.tsx b/web/src/components/app/contacts/filters/FilterBar.tsx
index 4842aef1d..427d326a5 100644
--- a/web/src/components/app/contacts/filters/FilterBar.tsx
+++ b/web/src/components/app/contacts/filters/FilterBar.tsx
@@ -76,7 +76,7 @@ const PROVIDERS: Option[] = [
         label,
         icon: <ProviderLogo id={id} size="xs" framed={false} />,
     })),
-    { id: "", label: "Not detected yet" },
+    { id: "", label: "Unknown or not checked yet" },
 ];
 
 // Optional pills, shown once added from the menu or when their value is set.
diff --git a/web/src/components/app/segments/filtersToSegment.ts b/web/src/components/app/segments/filtersToSegment.ts
index d4c278714..fbc387df0 100644
--- a/web/src/components/app/segments/filtersToSegment.ts
+++ b/web/src/components/app/segments/filtersToSegment.ts
@@ -43,9 +43,10 @@ export function filtersToSegment(f: SearchContacts, campaignID?: string): Segmen
         conditions.push({ field: "subscribed", operator: f.subscribed ? "is_true" : "is_false" });
     }
     if (f.verification_status) conditions.push({ field: "verification_status", operator: "in", values: [f.verification_status] });
-    // A segment enum has no empty value, so "not detected yet" does not carry over.
+    // A segment enum has no empty value, so "unknown" is reported rather than lost.
     const hosts = (f.mail_hosts ?? []).filter(Boolean);
     if (hosts.length > 0) conditions.push({ field: "mail_host", operator: "in", values: hosts });
+    if (f.mail_hosts?.includes("")) dropped.push("unknown email provider");
     if (f.min_campaigns !== undefined) conditions.push({ field: "campaign_count", operator: "gte", value: String(f.min_campaigns) });
     if (f.max_campaigns !== undefined) conditions.push({ field: "campaign_count", operator: "lte", value: String(f.max_campaigns) });
     if (f.created_after) conditions.push({ field: "created_at", operator: "after", value: isoDate(f.created_after) });
diff --git a/web/src/lib/api/models/app/contacts/SearchContacts.ts b/web/src/lib/api/models/app/contacts/SearchContacts.ts
index d8674638b..2f7e47321 100644
--- a/web/src/lib/api/models/app/contacts/SearchContacts.ts
+++ b/web/src/lib/api/models/app/contacts/SearchContacts.ts
@@ -18,7 +18,7 @@ export default interface SearchContacts {
     max_campaigns?: number;
     subscribed?: boolean;
     verification_status?: VerificationStatus;
-    // Contacts whose inbox is hosted by any of these; "" matches not detected yet.
+    // Contacts whose inbox is hosted by any of these; "" matches no known provider.
     mail_hosts?: MailHost[];
     created_after?: Date;
     created_before?: Date;
diff --git a/web/src/lib/api/models/app/contacts/SearchContactsResult.ts b/web/src/lib/api/models/app/contacts/SearchContactsResult.ts
index d5eb93ce3..b33c99097 100644
--- a/web/src/lib/api/models/app/contacts/SearchContactsResult.ts
+++ b/web/src/lib/api/models/app/contacts/SearchContactsResult.ts
@@ -60,6 +60,7 @@ export interface CampaignLeadCounts {
 export interface CampaignLeadProviderCounts {
     gmail: number;
     outlook: number;
+    // Includes checked domains with no known provider; they match like other.
     other: number;
     // Leads whose provider the background check has not read yet.
     undetected: number;