Dedicated server problem delivering emails to some servers
I just bought a dedicated server and was planning to do some email marketing, i was planning to send around 50,000 emails per day to targeted email addresses... its not spam as it is targeted to people in my country and they can easily unsubscribe from the list.
So i have setup postfix to handle the mail. I created the A and MX dns entries for my server and started doing some testing sending a couple of emails to my personal emails... things were working fine for 5 days until yesterday i suddenly stop receiving emails sent to my country's main mail system (lets say mycountry.com). Emails to gmail are working fine but sending emails to mycountry.com dont work. In the mail log i see this error:
debian postfix/smtp: 9DFF2378092: to=<email@example.com>, relay=mx3.mycountry.com[xxx.xxx.x.xx]:25, delay=4.5, delays=0.03/0/4.5/0, dsn=4.0.0, status=deferred (host mx3.mycountry.com[xxx.xxx.x.xx] refused to talk to me: 554 iron3.mycountry.com)
i read a bit on forums and someone advised me to create the PTR record to map my ipaddress to my hostname. I did that promptly and after 24hours i tried sending email again to mycountry.com but i still get the same problem and same error in log.
I've been looking around and ended up on SenderBase The IronPort Security Network where i see that my SenderBase reputation score for my ip address is "Poor"
i'm basically stuck now not knowing what to do to get the mail server to work properly. Any solutions for me please?