New to Mutt, unable to send messages in *any* attempted way

[Nathan Stratton Treadway]

On Thu, May 05, 2022 at 15:11:48 -0500, xtec at trimaso.com.mx wrote:
> I didn't mean email provider, but ISP internet service I'm connected to.
> And did test again: I connected to an internet network, did not specify 
> port in smtp_url, tried send email, and got:
> Could not connect to smtp.domain.tld (No route to host)
> Tried connecting to a different internet network, tried to send email 
> using *exact* command, without port, and *it succceeded*.

Some ISPs specifically block outgoing traffic on TCP port 25 (which is
the default port for "smtp:" traffic) -- one such example is documented
at:
   https://www.xfinity.com/support/articles/list-of-blocked-ports

My experience with Comcast residental-internet service is that the port
25 packets are simply dropped, so SMTP connection attempts hang and
eventually time out... but it seems that the ISP you used in your first
attempt instead blocks the traffic with a "no route to host" reply. 
This seems a bit misleading, but if port 587 traffic to that same host
does get through successfully while port 25 traffic does not, it seems
port-specific blocking of your traffic by that partiticlar ISP is the
most likely explanation....


						Nathan