Re: [gentoo-user] Technical imap mail question

[Tuomo Hartikainen]

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