Re: [gentoo-user] Technical imap mail question

[Mick]

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.

Port 25 (outgoing) is blocked by most domestic ISPs to guard against the 
millions of pawned botnets out there filling out inboxes with spam.

The question about a different SMTP server might have something to do with 
your ISP adding a new SMTP mailserver to their farm and configuring it 
properly this time as per RFC6409.  Although as Alan said, they probably 
rolled out whatever the chosen ISP package software vendor provided for them 
without knowing much about it, or why it is configured the way it is 
configured.

-- 
Regards,
Mick