1. ISPs need help routing mail to Exchange server over non-permanent Internet connection
I maintain a number of LANs, connected to the Internet via ISDN. I use
several ISPs but none of them have a good complete solution for mail
delivery to Exchange server when the network connection is intermittent.
Each time a PPP connection from the ISDN router is established any mail
queued at the ISP is delivered to the Exchange Server. E-mail header
information is not altered in the process.
I have found only one ISP in my area who attempts to dequeue the mail for
the domain when the PPP connect is established. It is a simple script to
send an ETRN to the server. This is a very useful thing to do and I am
suprised that so few ISPs do it.
However, this same ISP finds it necessary to insert a machine name in the
The problem comes in storing the mail when Exchange server is not available
with out bouncing it. One solution, which is a problem for me is the ISP
with domain.com is mail.ispname.com and the MX record for mail.domain.com
points to the Exchange server. All mail to domain.com goes to SMTP server
mail.ispname.com. mail.ispname.com finds an MX record for mail.domain.com
and attempt to forward the mail. When there is no route to this MX
address, the mail is stored until the another dequeue is attempted for
domain.com when the internet connnection is up. While this handles
routing, it requires that 2 smtp address be maintained for every Exchange
address used to deliver the mail.
Other ISPs associate to MX records with domain.com with different priority
numbers. The first MX address attempted is mail.domain.com (the Exchange
server). If there is no route to that address, the second MX address,
mail.ispname.com is used to deliver the mail. While this solves the
problem of having to maintain two SMTP address per user, my ISP who is
issuing an ETRN for each PPP connection, hasn't been able of figure out the
sendmail.cf configuration. With two MX record for domain.com, sendmail is
attempt to forward the mail to itself resulting the an error.
If any SMTP/sendmail.cf hacker out there know the solution to this it would
be real helpful.
Thanks is advance.
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