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Email authentication errors ​

This guide covers the two kinds of authentication problem: sign-in errors in an app, and DNS authentication failures that make receiving servers reject or spam your mail. You will also learn the safe checks for each.

Before you begin ​

Steps ​

Sign-in errors ​

  1. Check the username. Use the mailbox username shown in the Business Email Panel.
  2. Check the password. Passwords are case-sensitive. Sign in to webmail with the same password to test it.
  3. Update a recent password change in every app and device that uses the mailbox.
  4. Wait after repeated failures. Wait a few minutes before you try again, so the mailbox is not locked for longer.
  5. Check the server and ports. The server must be mail.apncloud.com, with port 993 for IMAP and port 465 or 587 for SMTP.

DNS authentication failures ​

  1. SPF fails: check that there is exactly one SPF record. See How to configure SPF.
  2. DKIM fails: check that the DKIM record matches the panel exactly. See How to configure DKIM.
  3. DMARC fails: check the DMARC record and the reports it sends. See How to configure DMARC.

Never switch encryption off

Do not turn off SSL/TLS or STARTTLS to fix a sign-in error. Do not accept an unknown certificate. Check the server name instead.

Expected result ​

The mailbox signs in from every app, and the authentication results in the message headers show SPF, DKIM and DMARC passing.

If something goes wrong ​

  • A certificate warning appears. The app cannot confirm that it is talking to mail.apncloud.com. Stop, check the server name in the app, and try again.
  • The problem continues after the DNS records are correct. DNS changes can take time to spread. Wait, then test again.
  • You cannot resolve it yourself. Contact support from the Client Area with the mailbox address, the app, the server and port, and the exact error text.

Last reviewed ​

2026-10-27