Quick answer
Change Thunderbird's incoming and SMTP ports separately, using the exact port and TLS mode supplied for the service. A custom number does not by itself make a connection secure.
Applies to
For an existing mailbox you are authorized to use in Thunderbird. For Interactive Online hosted mail, copy the exact secure settings from Email Accounts > Connect Devices. Account Hub and older Account Settings setup flows differ by Thunderbird version.
Steps
- Record the working hostnames, ports, TLS modes and affected account.
- Open Account Settings > Server Settings for the incoming server and update only the required values.
- Open Outgoing Server (SMTP), select the entry actually used by this identity and edit its matching port/TLS settings. Save.
Check the result
Test both send and receive. If several accounts share one SMTP entry, test each affected identity.
Troubleshooting and support
For connection failures, compare protocol, TLS mode, hostname and network access. Keep encryption enabled and use the mail provider's incoming and outgoing ports. A shell or control-panel login port is not a mail port.
If the problem continues, contact support from the account that owns the service. Include the domain, exact error, time and time zone, tool name, and a redacted screenshot. Keep passwords, private keys, cookies and private message content out of the ticket.
Video tutorial
The original video is preserved. Its interface or product version may differ from the written guidance above.
Related help
Official references
Written content reviewed November 1, 2026. Menu availability depends on the product version, permissions and service.
