On Sun, Sep 09, 2001 at 04:45:42PM -0700, Eric Paynter wrote:
> Some ISPs not only block SMTP based on IP, but also based on sender's
> address. Therefore, when domain-email-hosted customers try to send through
> their ISP's relay, it will not accept the mail. The whole concept of hosting
> domains and email when you are not an ISP is quite difficult to manage when
> considering problems like mail relaying.
Not only that, but some ISPs will block SMTP connections to any SMTP server but
their own, so even if you implement SMTP-AUTH or SMTP-after-POP there's no
guarantee that your users will be able to reach you.
I spend about half my life in other countries and use many different ISPs, and
it's always been somewhat of a trick to get my mail out. My solution has been
to run SMTP-AUTH on a non-standard port and connect to that (actually, I
usually just make an SSH connection to my server at home and write my mail from
there, but writing mail online can get expensive). That works fine for me, but
not all mail clients support it (particularly the non-standard port part), and
most of our users don't understand it. You wind up telling them, "Connect to
your ISP's mail server, but if they reject your mail because your e-mail
address isn't one of theirs, connect to our SMTP server but enter your user
name and password, and if your ISP blocks that, change the SMTP port number, if
your mail client supports it. Otherwise, you'll have to..."
I used not to be as sympathetic about roaming users ("Just use your ISP's SMTP
server!"), but it's becoming more difficult to be a multi-ISP roaming user and
get your mail out, what with envelope-sender checks and blocking outside SMTP
access and all, especially when you don't understand exactly how the whole
process of Internet mail works.
Chris
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