Mailbox Reconnection — when and how to reconnect
When you see a Reconnect Required badge on a mailbox — or the Reconnect Required banner on the dashboard — sending from that mailbox is blocked until you take action. This page explains exactly when WarmySender flags a mailbox for reconnection, what you should do, and what happens in the meantime.
When does a mailbox need reconnection?
A mailbox is flagged for reconnection when any of these conditions are true:
- The mailbox status is needs_reauth — set when a recent send rejected your credentials (e.g., SMTP 535 5.7.8 or 534 5.7.14), when an OAuth refresh token was revoked, or when the M365 admin disabled SMTP AUTH at the tenant level.
- The mailbox status is error AND the last error message indicates an authentication problem — e.g., "534-5.7.14 Please log in via your web browser" (Gmail requires re-authentication — generate a fresh App Password), "535 5.7.8 Authentication credentials invalid" (Zoho / IMAP password rejected), or "5.7.139 SmtpClientAuthentication is disabled for the Tenant" (Microsoft 365 admin must enable SMTP AUTH).
- The structured pause reason is one of: auth_failure, auth_errors, tenant_smtp_disabled, provider_block, hostinger_reauth_required, mailbox_disconnected. These are written by the warmup engine, the campaign send pipeline, and the OAuth token refresh job when they detect an unrecoverable auth state.
- Warmup is paused or in an error state AND the last error message is authentication-related. This catches mailboxes where warmup itself stopped sending because the provider rejected the credentials.
What should I do?
• On the Mailboxes page, click the Reconnect Required badge or open the affected mailbox's menu. The action you'll be prompted to take depends on the provider:
- Gmail / Google Workspace: click Update credentials and paste a fresh App Password — Gmail connects with an App Password over IMAP/SMTP, not a Google sign-in. App Passwords are often invalidated by a password change or a security review. Generate a new one at myaccount.google.com/apppasswords (2-step verification must be on) and save. This typically takes a minute or two.
- Outlook / Microsoft 365: click Reconnect with Microsoft to re-grant OAuth, or if the error is 5.7.139, ask your M365 administrator to enable Authenticated SMTP for your mailbox (see /documentation/smtp-tenant-disabled for the admin steps).
- Custom IMAP/SMTP (Hostinger, Zoho, Yahoo, Fastmail, self-hosted, etc.): click Update credentials and paste a fresh password or App Password. For providers that require App Passwords (Gmail-via-SMTP, Yahoo, iCloud, Outlook personal accounts with 2FA), generate a new one from your provider's security settings and update the SMTP/IMAP password fields.
- You can also use the dashboard's Reconnect Required banner. Click View all mailboxes and the Mailboxes page will open with the filter pre-applied to Needs Reconnect.
What happens in the meantime?
- Warmup pauses immediately for the affected mailbox. The mailbox is removed from the peer pool so other WarmySender customers' warmup emails don't bounce off your dead credentials, which would otherwise hurt their sender reputation.
- Active campaigns skip the affected mailbox for new sends. The campaign itself stays running; it just rotates to your other healthy mailboxes. If this is the only mailbox attached to a campaign, the campaign pauses until reconnection.
- Inbox sync (replies, opens, bounces) pauses for the mailbox until credentials are restored. Once you reconnect, the next inbox-sync cycle picks up any unread mail that arrived during the gap.
- No data is lost. The mailbox row, its warmup history, its campaign membership, and all events stay intact. Reconnecting restores everything.
How long does reconnection take?
- For Outlook / Microsoft 365 (OAuth): typically under a minute end-to-end. Click the badge, complete Sign in with Microsoft, and the badge clears as soon as the next health check runs (within seconds).
- For App Password / credential providers (Gmail, Hostinger, Zoho, custom IMAP): same — the new App Password is tested at save time and the badge clears immediately if the test send succeeds.
- For the M365 tenant-disabled case (5.7.139): the badge clears within 60 seconds of your admin saving the Authenticated SMTP setting. Microsoft typically propagates the change in under a minute, but rare tenants take up to 30 minutes.
Note: WarmySender will never email you to reconnect a mailbox — the in-app surface is the source of truth. If you're worried about phishing, anyone asking you to "reconnect your mailbox" via email is not us. Always open warmysender.com directly to take action.