For providers without native OAuth: connect via IMAP/SMTP with host, port, and app password. Full sending and reply detection work; some health signals are reduced versus API connections.
What you need
IMAP host/port, SMTP host/port, username, and an app-specific password (most providers require app passwords when 2FA is on). Settings → Mailboxes → Add → IMAP/SMTP.
Limitations vs API connections
Reply detection polls rather than streams (1–2 minute latency vs seconds), and some provider-side reputation signals aren't visible. Deliverability monitoring still works via seed testing and bounce analysis.
Common setup errors
Wrong port/TLS combination (use 993/SSL for IMAP, 587/STARTTLS for SMTP in most cases), a regular password instead of an app password, and provider-side IMAP disabled by default (enable it in the provider's settings).
When to choose IMAP
Only when Google/Microsoft OAuth isn't available — regional providers, custom mail servers. If the mailbox is Gmail or M365 under the hood, always use the native connector.
