dovecot warns (non-fatal) "invalid EHLO response line: Unexpected character in EHLO keyword" connecting to submission relay ?

[Alec Moskvin]

On Friday 25 September 2020 12:56:50, PGNet Dev wrote:
> I'm setting up an alternative submission relay host for dovecot.  Atm, it's pointing @ fastmail.com.
>
> with dovecot config,
>
> 	submission_relay_host       = smtp.fastmail.com
> 	submission_relay_port       = 465
> 	submission_relay_ssl        = smtps
> 	submission_relay_ssl_verify = no
> 	submission_relay_trusted    = yes
> 	submission_relay_user       = 'acctID at mydomain.com'
> 	submission_relay_password   = 'acctPWD'
>
> submission relay via dovecot proxy works as expected -- mail's delivered/received by intended recipient.
>
> in local dovecot logs I notice
>
> 	==> /var/log/dovecot/dovecot.log <==
> 	2020-09-24 16:22:19 submission(recipient at example.com)<xxxxxxxxxxxxxxxx>: Warning: smtp-client: conn smtp.fastmail.com:465 (66.111.4.140:465) [1]: Received invalid EHLO response line: Unexpected character in EHLO keyword
>
> at debug level
>
> 	==> /var/log/dovecot/dovecot-debug.log <==
> 	2020-09-24 16:22:19 submission(recipient at example.com)<xxxxxxxxxxxxxxxx>: Debug: smtp-client: conn smtp.fastmail.com:465 (66.111.4.140:465) [1]: command EHLO: Got reply (1/1): 250 mail.messagingengine.com PIPELINING SIZE 73000000 AUTH DIGEST-MD5 CRAM-MD5 NTLM LOGIN PLAIN AUTH=DIGEST-MD5 CRAM-MD5 NTLM LOGIN PLAIN ENHANCEDSTATUSCODES 8BITMIME (1 commands pending, 0 commands queued)
>
> it's clearly non-fatal, simply a warning.
>
> i certainly do _not_ see this with every relay host, so suspect it's unique to fastmail's EHLO response. at least within the set of hosts I've tested.
>
> i'd like to find/fix it ... either at my dovecot instance, or @ fastmail.
>
> what's specifically invalid about
>
> 	250 mail.messagingengine.com PIPELINING SIZE 73000000 AUTH DIGEST-MD5 CRAM-MD5 NTLM LOGIN PLAIN AUTH=DIGEST-MD5 CRAM-MD5 NTLM LOGIN PLAIN ENHANCEDSTATUSCODES 8BITMIME
>
> by dovecot's 'measure'?

The "=" in AUTH=PLAIN.

See: https://dovecot.org/pipermail/dovecot/2020-September/119854.html

    $ openssl s_client -connect smtp.fastmail.com:465
    ...
    220 smtp.fastmail.com ESMTP ready
    ehlo asdf
    250-smtp.fastmail.com
    250-PIPELINING
    250-SIZE 71000000
    250-ENHANCEDSTATUSCODES
    250-8BITMIME
    250-AUTH PLAIN LOGIN
    250 AUTH=PLAIN LOGIN

Thanks,
Alec