Our Live IP is blocked by cbl.abuseat.org.
Well, I am using sendmail server as a mail server (MTA) on RHEL5. Our main firewall is sending the smtp traffic with the IP same as live IP of sendmail server. sendmail server configuration is fine according to CBL links below
Here is the output of helocheck
----- The following addresses had permanent fatal errors -----
(reason: 550 HELO for IP XX.XXX.XX.XXX was "MAIL.MYDOMAIN.COM")
both nslookup and reverse lookup are fine.
The MX entry is the same as MAIL.MYDOMAIN.COM in a hosting company where MAIL.MYDOMAIN.COM is regeistered as a subdomain of MYDOMAIN.COM.
We send all emails from a script that collects information from DB server and then send all emails from sendmail server (MAIL.MYDOMAIN.COM).
Well, as we are using linux machines so i cant expect that they are infected with viruses and trojans. Our company business is like that we send thousands of emails to all our clients in all over the world.
Well, I am not sure but can someone help me to understand that may be one of the following can be the cause of this?
1. the emails we sent to customer are e.g. [ From: firstname.lastname@example.org], emails are sent from mail.mydomain.com (sendmail server). Is this can be the issue? as sending email source (mail.mydomain.com/firewal
l) IP is different from mydomain.com. So whenever somewhere in middle of the way emails are checked then the reverse NS Lookup of mail server (mail.mydomain.com) points different IP than that is in the From address of email@example.com?
2. Any relay issue?
3. We dont receive emails on sendmail server so can it be the reason that whenever any ISP receive emails from this server it cant get back to it?
I am trying to fix this issue from last three four days. Can someone help me to sort out this issue?