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Thunderbird: selected authentication method is not supported

Compare server, port, TLS mode and authentication when Thunderbird rejects the selected method.

Source date: 5 November 2026Editorial team: KAN KAI WORKSEditorially updated:

Quick answer

“Selected authentication method is not supported” points to a mismatch between the server and authentication method; it does not prove that the password is wrong. Check incoming mail and SMTP separately, comparing server, port, connection security and method with provider guidance. Successful webmail login does not validate those protocol settings. Change the evidenced mismatch while preserving the account, messages and secure connection settings.

Source basis: Q1 · Q2

Applies to
Applies to Thunderbird IMAP, POP and SMTP accounts with provider-specific authentication. Only the original Spectrum thread title was available, without a verified resolution.
How to verify the result
Receiving works and a clearly marked test message is delivered through the intended sending identity, with the expected connection security and authentication retained.
Your first check

Do the server, connection security and authentication method match?

Compare the exact combination with the provider’s current instructions. A correct password cannot fix an unsupported method at the selected endpoint.

Thunderbird reports selected authentication method is not supported. Sending, receiving or both may fail. The useful first check is the combination of endpoint and authentication method. Mozilla treats server, port, connection security and authentication as related settings supplied by the email provider. Q1

Separate credentials from method selection

A password can be correct while the contacted server does not support the selected method. An incorrect hostname can also produce an unexpected response. Avoid cycling through every available option. Establish the documented configuration for your exact account type before making changes.

Identify the failing connection

  1. Test sending and receiving separately. If existing mail downloads but a harmless outgoing message fails, start with SMTP. If retrieval fails, record whether the account uses IMAP or POP. These observations narrow the settings that actually matter.
  2. Obtain current provider instructions. Compare hostname, port, TLS or STARTTLS mode, username format and authentication. Do not borrow server values from a different provider's forum thread. A working webmail login verifies that access path, not these protocol settings.
  3. Check the SMTP assignment. A Thunderbird identity can use a particular outgoing-server entry. Inspect the entry actually assigned to the affected identity rather than another similarly named default server. Mozilla explicitly includes this check in its sending guide. Q2
  4. Preserve the first response. Record whether failure occurs before or after authentication. Where administrative logs are available, initially collect server, timestamp and error code. Passwords and full message bodies are unnecessary for that comparison.
  5. Test one documented correction. Change only the mismatched setting. Then verify receipt and delivery using a clearly marked message. If OAuth is required, also confirm that its intended authorisation sequence completes.

Do not infer profile damage from this message

The error does not establish that mail data is lost. Removing the account, clearing every saved password or disabling TLS changes several unrelated variables. If the documented settings still fail, ask the provider to confirm the exact endpoint and supported authentication methods for this account.

For handoff, prepare the provider, account type, Thunderbird version, sanitised settings and separate send/receive results. The candidate originated in a Spectrum support thread whose resolution could not be reliably refreshed. This guide therefore does not assert unverified Spectrum-specific server values. Q3

Frequently asked questions

Should I select Normal password?

Only when the provider specifies that method for the secure connection. The error alone does not determine the correct replacement.

Why does webmail still work?

Webmail uses a different sign-in path from IMAP, POP or SMTP and does not validate those protocol settings.

Describe your case

Support with this issue

We can review account settings and SMTP mapping without prematurely replacing your profile.

Describe your case →Related service: Data & improvements

Sources