Re: [gentoo-user] Fully-Defined-Domain-Name for nullmailer

[Grant Taylor <gtaylor@gentoo.tnetconsulting.net>]

On 4/13/22 6:31 AM, n952162 wrote:
> Unfortunately, I get a 550 from my network provider for all of these:
> 
>  1. me
>  2. localdomain
>  3. net
>  4. web.de
> 
> So, how does thunderbird do it?

I don't know what name Thunderbird uses in it's HELO / EHLO command(s). 
Though it shouldn't matter much which name is used.

The important thing should be that the SMTP client, be it Thunderbird or 
nullmailer or something else, should authenticate to the outbound relay 
/ MSA.  The MSA should then use that authentication as a control for 
what is and is not allowed to be relayed.

Nominally, the name used has little effect on the SMTP session.  However 
there is more and more sanity checking being applied for server to 
server SMTP connections.  Mostly the sanity checking is around that a 
sender isn't obviously lying or trying to get around security checks. 
These attempts usually take the form of pretending to be the destination 
or another known / easily identifiable lie.

Mail servers that send server to server traffic actually SHOULD use 
proper names that validate.  Clients shouldn't need to adhere to as high 
a standard.  I consider nullmailer to be a client in this case.



-- 
Grant. . . .
unix || die