mailserver being added to blocklists


My server runs Virtualmin on top of a debian server.
The server has about 8 dedicated IP’s assigned in 2 ranges.
The main problem, I think, is that an nslookup of the different MX domains on the server will point to different IP’s, but the e-mails are always sent from one specific IP. That IP I’m using as a DNS server IP and the PTR records are set accordingly. Due to this, several mail servers (including yahoo and microsoft) are blocking mails from my server.
I need a quick fix how to force postfix to send e-mails from a different IP.


You will need to provide more details as right now it looks like you are a spammer. Not sure why we would help you.

Hey Diabolico,

Sadly not. Some providers (yahoo, microsoft) block senders if the PTR record does not match the hostname specified in the SMTP banner. It’s a technique to avoid spam, sadly it’s not by default configured in Virtualmin.

I found the problem and could solve it by adding the following parameter to the postfix/

[blockcode]smtp_bind_address = [/blockcode]

This line defines which IP to use to send from. This way I could force Postfix to use the correct IP that matches the PTR record for that server.

I hope this may help somebody in the future.

Why dont you sort rDNS for all IPs? You can do that from the server control panel or just open a ticket and your host will do this in few minutes. Another thing, Yahoo, Hotmail, Gmail… will never blacklist you because you sent few emails without rDNS. That must be some huge amount of emails coming from your IP(s) to be blacklisted. Earlier mentioned email providers use their internal blacklist and to get removed sometimes can take months.

To know what is going on you should check your mail logs and see what code you get for rejected emails, it could be permanent ban or just temporary in which case you will get removed in few days if you dont spam anymore.

Last but not least, Gmail and Hotmail (could be others but i’m not sure) ask you to have all in place and that means: valid SPF record, valid DKIM and rDNS. If you miss something pretty soon you will find yourself on their list. Just pay attention that with your IP they can put your domain on the same list.