We've started receiving spam with spoofed addresses from our own domain. So I'm trying to get my PTR and SPF records etc correct to prevent it. We're running Exchange 2010 on site with one server configured to run all roles. Our SAN certificate for Exchange includes: webmail.domain.org and autodiscover.domain.org
I currently have the following records in my external DNS (The SPF record was generated using Microsoft's Sender ID Framework Wizard):
domain.org A 18.104.22.168 mail.domain.org A 22.214.171.124 mail.domain.org PTR 126.96.36.199 domain.org MX 0 mail.domain.org webmail.domain.org A 188.8.131.52 webmail.domain.org PTR 184.108.40.206 autodiscover.domain.org A 220.127.116.11 _autodiscover._tcp.domain.org SRV 0 0 443 webmail.domain.org domain.org TXT "v=spf1 mx ip4:18.104.22.168 a:webmail.domain.org ptr:webmail.domain.org ptr:99-99-99-99.static.virginm.net mx:mail.domain.org a:99-99-99-99.static.virginm.net ~all"
If I do a reverse lookup using Google's DNS server I get a response from our ISP similar to:
Which doesn't match the domain being presented by my mail server.
My internal DNS has the following records:
domain.org A 192.168.0.123 mail.domain.org A 192.168.0.234 webmail.domain.org A 192.168.0.234 mailserver.domain.internal PTR 192.168.0.234 autodiscover.domain.org CNAME webmail.domain.org _autodiscover._tcp.domain.org SRV 0 0 443 webmail.domain.org
My questions are:
1) Do I need to add an MX record to my internal DNS?
2) Do I need ask my ISP if they're able to change their PTR to mail.domain.org?
3) Our users access OWA via webmail.domain.org. Should I change my MX record to webmail.domain.org and get rid of mail.domain.org completely? If not, does mail.domain.org need to be on my SAN certificate?
4) My FQDN response to HELO/EHLO is: mailserver.domain.internal. Do I need to change this to match the domain on my certificate or my MX record? or leave it as it is?
5) Do I need to make a different SPF record with internal IP addresses and add it to my internal DNS?
6) Is the SPF record I have generated correct?
7) Is there anything else that I need to change which I haven't asked about? lol
I've tried to give as much information as possible, but if you need anything else please ask.