Re: smtpmail-send-queued-mail fails with error 504 5.5.2

[rameiko87@posteo.net]

>> which should instead only be reserved for message-id's (as the
>> description of this variable says. Does it happen somewhere else too?
>> this is the second thing to fix).
> 
> How to fix something that we don't know about?

Is there any way to check where the variable message-user-fqdn is being 
used?

Also, I understand from your messages that when message-user-fqdn is nil 
then the Message-ID's are built with domain set to the value of the 
domain in user-mail-address, no matter whether this is a valid address 
or not. In the preceding sentence, by domain I mean everything to the 
right of the at-sign. Is this correct?

When I set message-user-fqdn instead, are the Message-ID's always built 
by using the message-user-fqdn regardless of the value of 
user-mail-address?

And then when message-user-fqdn is nil and user-mail-address is the 
default (that is user@fedora), then does Message Mode attempt sending to 
this invalid email address and shows an error, or does it modify the To: 
to some valid email address?