diff --git a/internal/api/handler/unibox.go b/internal/api/handler/unibox.go
index 62e5880e..a6b5c234 100644
--- a/internal/api/handler/unibox.go
+++ b/internal/api/handler/unibox.go
@@ -75,6 +75,12 @@ func (h *Handler) GetUniboxIncoming(c *gin.Context) {
 		params.Sender = &from
 	}
 
+	// Address filter: conversations with this person in either direction
+	// (they sent it or we sent it to them). Powers the compose history panel.
+	if address := c.Query("address"); address != "" {
+		params.Address = &address
+	}
+
 	// Parse subject filter
 	if subject := c.Query("subject"); subject != "" {
 		params.Subject = &subject
diff --git a/internal/infrastructure/db/migrations/000071_unibox_to_addr_index.down.sql b/internal/infrastructure/db/migrations/000071_unibox_to_addr_index.down.sql
new file mode 100644
index 00000000..b1006997
--- /dev/null
+++ b/internal/infrastructure/db/migrations/000071_unibox_to_addr_index.down.sql
@@ -0,0 +1 @@
+DROP INDEX IF EXISTS idx_unibox_emails_to;
diff --git a/internal/infrastructure/db/migrations/000071_unibox_to_addr_index.up.sql b/internal/infrastructure/db/migrations/000071_unibox_to_addr_index.up.sql
new file mode 100644
index 00000000..e031dc72
--- /dev/null
+++ b/internal/infrastructure/db/migrations/000071_unibox_to_addr_index.up.sql
@@ -0,0 +1,4 @@
+-- Compose needs "conversations with this address" lookups that match either
+-- side of the exchange. from_addr already has a GIN index; mirror it on
+-- to_addr so the address filter and mailbox-affinity scoring stay indexed.
+CREATE INDEX IF NOT EXISTS idx_unibox_emails_to ON public.unibox_emails USING gin (to_addr);
diff --git a/internal/models/unibox.go b/internal/models/unibox.go
index 8a9217b1..f8ce4069 100644
--- a/internal/models/unibox.go
+++ b/internal/models/unibox.go
@@ -156,7 +156,11 @@ type MailSearchResult struct {
 }
 
 type MailSearchParams struct {
-	Sender  *string
+	Sender *string
+	// Address matches either side of the exchange (from_addr OR to_addr),
+	// giving "every conversation with this person" regardless of direction.
+	// Substring match on the raw header entries, like Sender.
+	Address *string
 	Unseen  *bool
 	Subject *string
 	Since   *time.Time
diff --git a/internal/repository/pg_unibox.go b/internal/repository/pg_unibox.go
index e7b72a57..efe8480b 100644
--- a/internal/repository/pg_unibox.go
+++ b/internal/repository/pg_unibox.go
@@ -415,6 +415,17 @@ func (r *uniboxRepository) Search(ctx context.Context, orgID, userID uuid.UUID,
 		argPos++
 	}
 
+	if params.Address != nil && *params.Address != "" {
+		// Either direction: the contact as sender OR as recipient, so the
+		// result is the full back-and-forth with that address.
+		inner += fmt.Sprintf(` AND EXISTS (
+				SELECT 1 FROM unnest(ue.from_addr || ue.to_addr) AS f(addr)
+				WHERE f.addr ILIKE '%%' || $%d || '%%'
+			)`, argPos)
+		args = append(args, *params.Address)
+		argPos++
+	}
+
 	if len(params.EmailAccountIDs) > 0 {
 		inner += fmt.Sprintf(` AND ue.email_id = ANY($%d)`, argPos)
 		args = append(args, params.EmailAccountIDs)