On 2015-10-15 23:01, Mick wrote: > On Thursday 15 Oct 2015 18:04:22 walt wrote: > > My ISP recently started offering imap email service in addition to > > the pop3/smtp servers they've always had, so I decided to try it. > > > > I was surprised to see that they recommend using a different smtp > > server name when setting up my mail client, and they even offer the > > option of using port 587 instead of 465 if I prefer it. > > > > Why would I use a different smtp server if I'm now using imap? I use > > smtp to send mail, and imap to read it, right? Why not use the same > > smtp server in either case? > > > > (The different server names actually resolve to the same IP address, so > > the distinction seems to be more theoretical than real, but the theory > > is what puzzles me.) > > > > Thanks. > > Port 587 is for TLS and is the proper port to be used by MSAs as per RFC6409. > > Port 467 on the other hand is for SMTPS: vanilla SMTP at the application > level, but the communication to the server is still secured at the transport > layer with SSL. This was an IANA attempt to provide a port for secure email > communication pre-STARTTLS days. Today I think may be used for other > purposes, but I am not sure if it is TCP or UDP streaming.
As a clarification: port 587 *may* be used with STARTTLS while port 465 is the actual SSL/TLS port. -- Tuomo Hartikainen
