Memo to a beginner postmaster

I would like to give some general tips for email administrators. I hope it will be useful for beginners, but a reminder will be experienced to check the status of their systems for normal, unhindered email circulation, as well as for better spam filtering with a minimum of false positives.

1. Be sure to register the reverse zone for your mail server (ptr record). This is not so difficult to do. In most cases, it is enough to write to your Internet service provider. Further, he will either write in his dns or delegate your zone to you (in-addr.arpa).
2. Try to keep up to date the PTR record with the A pointed to by the MX record.
3. Use fqdn in hello / ehlo greetings
4. Check that you are not using openrbl.org in RBL lists. This service has long been closed and blocks all recipients.
5. Enable the ability to work over a secure tls connection. Even with a self-signed certificate, but it has the correct common name that matches your PTR record. Use both SMTP over SSL and submission services.
6. Do not prohibit DSN (delivery status notification) in your mailers, they significantly allow you to simplify the solution of emerging problems.

These are very short tips, but based on their experience, no more than 30% of mail servers in the CIS can withstand them.

PS If necessary, I will write how to implement this with respect to postfix.