On 9/29/19 8:04 PM, Hugo Florentino wrote: > El vie, 27-09-2019 a las 12:22 -0400, Viktor Dukhovni escribió: >> [...] >> >> This makes no sense. Portable devices use ports 587 or 465 with all >> the other providers. And there's no "change ports constantly", they >> just use the same submission port. >> >> Remote MTAs connect to port 25, submission clients (MUAs) connect >> to port 587. >> > Suppose ISP imposes restrictions so the only port open either for SMTP > or submission must be TCP 25. What then? > > If an ISP allows you to run a mail server but won't allow access to 587/465 then you need a new ISP with a clue.
Some ISPs will block OUTGOING port 25 to prevent you from being a spammer, requiring you to use their SMTP server for outgoing SMTP transport, but I haven't heard of one that blocks 587 or 465 unless they don't allow you to run servers and just block most server ports. -- Richard Damon
