fix: show the via badge only when the identity's name adds something to the sender

src/components/email/MessageHeader.tsx

@@ -12,7 +12,7 @@ import { useLocaleStore } from '../../stores/locale-store';
 import { useAccountKeywordDefs } from '../../stores/keywords-store';
 import { emailDisplayDate, formatHeaderDate, formatHeaderTime, formatFullDateTime } from '../../lib/email-date';
 import {
-  deriveHeaderInfo, deliveryDeltaMs, formatDelta, isAuthenticationSpoofed, findReceivingIdentity,
+  deriveHeaderInfo, deliveryDeltaMs, formatDelta, isAuthenticationSpoofed, findReceivingIdentity, viaIdentityNameShown,
   getSenderVerification, describeSenderVerification,
   type AuthenticationResults, type EmailHeaderInfo,
 } from '../../lib/email-headers';
@@ -138,7 +138,7 @@ export function MessageHeader({ email, identities, headerInfo, onToggleStar, onA
     if (spoofed || identities.length === 0) return null;
     const fromEmail = from?.email?.toLowerCase();
     const sentAs = fromEmail ? identities.find((i) => i.email?.toLowerCase() === fromEmail) : undefined;
-    if (sentAs) return { identity: sentAs, direction: 'from' as const };
+    if (sentAs) return viaIdentityNameShown(sentAs, from) ? { identity: sentAs, direction: 'from' as const } : null;
     const received = findReceivingIdentity(identities, email);
     if (received && identities.length > 1 && received.id !== identities[0].id) {
       return { identity: received, direction: 'to' as const };
@@ -258,7 +258,7 @@ export function MessageHeader({ email, identities, headerInfo, onToggleStar, onA
             <View style={[styles.badge, { backgroundColor: c.primaryBg }]}>
               <Text style={[styles.badgeText, { color: c.primary }]}>
                 {viaIdentity.direction === 'from'
-                  ? t('identities.badge.identity_short', 'via {name}', { name: viaIdentity.identity.email })
+                  ? t('identities.badge.identity_short', 'via {name}', { name: viaIdentity.identity.name })
                   : t('email_viewer.received_via', 'to {name}', { name: viaIdentity.identity.email })}
               </Text>
             </View>

src/lib/__tests__/via-badge.test.ts

@@ -0,0 +1,25 @@
+import { describe, it, expect } from 'vitest';
+import fs from 'node:fs';
+import path from 'node:path';
+import { viaIdentityNameShown } from '../email-headers';
+
+// Mail sent as one of the user's identities read "Ann <ann@x>" with a
+// "via ann@x" badge: the sender's address a second time (webmail
+// email-identity-badge.tsx shows the identity's name, and only when it adds
+// something).
+
+describe('"via" badge', () => {
+  it("shows the identity's name only when it differs from what the sender line says", () => {
+    const from = { name: 'Ann Smith', email: 'ann@example.org' };
+    expect(viaIdentityNameShown({ name: 'Support', email: 'ann@example.org' }, from)).toBe(true);
+    expect(viaIdentityNameShown({ name: 'Ann Smith', email: 'ann@example.org' }, from)).toBe(false);
+    expect(viaIdentityNameShown({ name: 'ann@example.org', email: 'ann@example.org' }, from)).toBe(false);
+    expect(viaIdentityNameShown({ name: '', email: 'ann@example.org' }, from)).toBe(false);
+  });
+
+  it("names the identity, not its address, in the reader's badge", () => {
+    const header = fs.readFileSync(path.resolve(__dirname, '../../components/email/MessageHeader.tsx'), 'utf8');
+    expect(header).toMatch(/'via \{name\}', \{ name: viaIdentity\.identity\.name \}/);
+    expect(header).toMatch(/viaIdentityNameShown\(sentAs, from\)/);
+  });
+});

src/lib/email-headers.ts

@@ -97,6 +97,21 @@ const SPF_SEVERITY: Record<SpfResult, number> = {
   pass: 0,
 };
 
+/**
+ * Whether "via <identity>" on a message sent as one of the user's identities
+ * tells the reader anything: only when the identity's name differs from its
+ * address, the From address and the name already shown as the sender, so it
+ * no longer reads "ann@x via ann@x" (webmail email-identity-badge.tsx).
+ */
+export function viaIdentityNameShown(
+  identity: Pick<Identity, 'name' | 'email'>,
+  from: { name?: string | null; email?: string | null } | undefined,
+): boolean {
+  const name = identity.name?.trim();
+  if (!name) return false;
+  return name !== identity.email && name !== from?.email && name !== from?.name;
+}
+
 /**
  * Whether the authentication results indicate the visible From identity can't
  * be trusted (i.e. the message is likely spoofed). Used to suppress UI that