A certificate warning usually means the application is connecting to a hostname that is not covered by the mail-server certificate.
Applies to: Hosting mailbox IMAP and SMTP connections
Important: Do not permanently accept an unexpected certificate or install an unknown profile merely to make the warning disappear.
Correct the hostname
- Cancel the warning without submitting the mailbox password if the hostname is unexpected.
- Open the Customer Portal service details or hosting welcome email.
- Copy the assigned secure server hostname exactly.
- Use that hostname for both incoming and outgoing mail.
- Confirm IMAP uses port
993with SSL/TLS and SMTP uses port587with STARTTLS. - Reconnect and inspect the certificate name and validity period.
Common problems
| Symptom | Likely cause | What to do |
|---|---|---|
| The warning continues with the assigned hostname. | A local proxy, security product, captive portal or incorrect system clock may be intercepting validation. | Set the device time automatically, test another trusted network and record the certificate issuer/name for Support. |
| The warning appears only on one device. | That device has a stale account profile or trust setting. | Compare its hostname and security settings with a working device; recreate only after preserving local-only mail. |
Related articles
- Hosting email settings for any email application
- Add a hosting mailbox to a mobile email application
- Add a hosting mailbox to a desktop email application
- Test IMAP and SMTP settings separately
- Recognise a fake Tudor Internet login or payment message
Last reviewed: 2026-07-25.
