Test IMAP/SMTP credentials before importing (Connection tester)
Try a mailbox's SMTP and IMAP settings and optionally send a test email without saving anything, to check credentials before an import or to diagnose one that stopped connecting.
Where: Mailboxes → "Connect Mailbox" → "Any IMAP / SMTP", or the "connection tester" link in the Import Mailboxes dialog (page titled "Connection tester" under Diagnostics)
How to do it
- Open the Connection tester from Connect Mailbox → Any IMAP / SMTP, or from the link in the Import Mailboxes dialog.
- Pick a "Provider preset" (Gmail / Google Workspace, Outlook / Microsoft 365, Mailgun, Brevo, SendGrid, Postmark, Amazon SES) to fill host, port and security — or pick "Or an imported mailbox" to load an existing sender's settings (everything except the password).
- Fill in the SMTP Server, Port, Security (Auto (from port), STARTTLS, TLS (implicit), None), Username and Password. Tick "Also test inbound" to test IMAP too; untick "Same as SMTP" if IMAP uses a different password.
- Enter From name, From address and (for a send test) To address.
- Click "Test connection" to check SMTP (and IMAP) without sending, or "Send test email" to actually deliver a message. Read the Result panel: "SMTP connected" / "SMTP failed" with the server's reason, and "Message accepted" with the accepted/rejected addresses.
Good to know
- Nothing you enter here is saved — the page says so and it is true. To connect the mailbox, import it via CSV.
- Gmail requires an app password, not the account password (Google Account → Security → 2-Step Verification → App passwords), and it must be the app password for that exact account, pasted without spaces.
- Relay presets (Mailgun, Brevo, SendGrid, Postmark, Amazon SES) are send-only, so the IMAP section switches itself off for them.
- Auto security follows the port: 465 → implicit TLS, 25 → none, other SMTP ports → STARTTLS; 993 → TLS for IMAP, otherwise STARTTLS.
- Each check waits up to 15 seconds to connect and retries once on a timeout.