Mail Server Block by Spamguard
We have our internal and external dns. External dns using public IP. Our mail ip server has been block by spmaguard on our client site. It said our mail ip is spammer.
We already remove from blocklisted on our client but after a few days it happen again. vendor of spamguard said need to do checking on our site. But still we do not know how to secure it. Our mail using port25 to send mail. Please give suggestion to me. Can be dns using by public people and send mail bomber? Hope you guys here can assist me.