[Dovecot] Thunderbird STARTTLS error

[Ken Stevenson]

On 2012-05-08 14:17, Markus Fritz wrote:
> Hello,
>
> the error is still present:
> May  8 19:47:18 opsys dovecot: imap-login: Disconnected (no auth
> attempts): rip=82.113.119.140, lip=78.46.216.126
>
> Whenever I start a session with openssl to STARTTTL (Server:
> mail.opsys.de) the handshake is successfull. Also I am able to login
> to my account via 1 login.
> In Thunderbird port 993 for SSL/TLS works correct, only STARTTLS on
> port 143 isn't working properly.
> The cert is Class 1 and signed by StartCom Ltd..
> Dovecot.conf (for viewable reasons of this mail pasted):
> http://pastie.org/private/bmrymyuo16ohzxdahf0nq
> And here openssl output: 
> http://pastie.org/private/3rpgll2s7hblev9ozpcq8w
> Note the 'Verify return code: 21 (unable to verify the first
> certificate)' in the output...
>
> Thanks for helping, I am working on this problem since 3 days.
>
> Kind regards
>
> Markus Fritz

How about this:

Note: If you receive an error that looks like:

  454 TLS not available due to temporary reason', Port: 25, Secure(SSL): 
Yes, Server Error: 455, Error Number: 0x800CCC7F

or anything similar, it is because your Norton AntiVirus Email Scanning 
or other Anti-Virus software is scanning your outgoing email. Shut off 
the 'Scan outgoing Email' option and it should work.

It came from here:

https://cs.stanford.edu/computing-guide/email/client-settings