I believe that all the major email servers will look at the following before they decide to mark a received email as spam or not.
1. Mx record.
2. SPF record.
3. DKIM signature.
4. SMTP authentication.
5. Email from SSL ports.
6. Email message check to bayesian.
Is there any other things that an ordinary email server will check for?
Because my email server passed all the above but still my emails are marked as spam by leading email servers.
From my previous question I felt adding a forwarder to SMPP gateway will be better. How can I start my own SMPP service? Do it requires any hardware? Do any experts here know about SMPP?
Rather than purchasing SSL I would create a SSL certificate. Of course my SSL certificate will not be useful that browsers show "Un-trusted SSL". Can I use Self Signed SSL to my mail server to send and receive emails? By using self signed SSL do it interrupt users work saying "you are using un-trusted SSL certificate"?
Will it be useful?
And I believe that adding SSL to mail server for email exchange will change my port numbers from 25, 110, 143 to 465, 995, 993 Am I right?
I am getting an error in hMailServer log that some other application is using the ports 25 and 110 please make sure that they are disabled How to find which application is using these port?