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Want to set up PTR record(s) to handle the following:

Site with mail server (Exchange 2010) has three Internet connections, with the firewall handling load balancing.

I know that if the Internet connection with the IP in the MX record goes down, then no email will be received. Would still like to send email if this happens.

Have read some advice for setting up a PTR record for one IP.

If I bind the email to the same IP as the MX record, and create a PTR record for that IP, am assuming that if that particular connection goes down, then any outgoing email sent via the other connections will fail a PTR lookup and be marked as spam.

Do you know a way around this?

Thanks

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Not a complete answer, but you can have multiple MX records, one for each IP address, and a sender will try them in the order you specify in the priority field. –  Flup Mar 14 '13 at 8:31
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2 Answers

up vote 0 down vote accepted

You can have as many PTR records pointing to one domain as you want. I'd set them up as slightly different names, just because adding multiple A records for one domain means that the address returned for that name might not be the same one with which the server is connecting.

This MX setup will work nicely on the incoming side, but as your mailserver will only identify itself as one of these domain names, the reverse lookup may not function exactly as you'd like it.

An SPF record would probably help to resolve some of the situations:

v=spf1 mx -all would verify that any server with an MX record in your domain can send mail..

mail1.mail.com IN A 1.2.3.4
mail2.mail.com IN A 1.2.3.5
mail3.mail.com IN A 1.2.3.6

mail.com. IN MX 10 mail1.mail.com.
mail.com. IN MX 20 mail2.mail.com.
mail.com. IN MX 30 mail3.mail.com.

4.3.2.1.IN-ADD.ARPA PTR mail1.mail.com
5.3.2.1.IN-ADD.ARPA PTR mail2.mail.com
6.3.2.1.IN-ADD.ARPA PTR mail3.mail.com

BTW, you could always use an external relay for your mail, it would probably be available over any of the three connections..

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You can add some ptr records that will point to all of your outgoing connections and they will verify that this is good sender for remote servers.

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