Most of the time Postfix is configured with self signed certificate which works well because mostly certificate validation is not required by MTAs. Though it can be useful for applications or mailbox users connecting to central MTA to delivery of emails.
You can either buy SSL certificate from your provider or use letscrypt.org free certificates(needs to be renewed every 3 months). In this guide, i will use letencrypt certificate for my mx host console.postfix.io.
I use letsencrypt utility to manage certificate for my domains, below command will generate standalone certificate for my host. letsencrypt certonly --standalone -d console.postfix.io
Congratulations! Your certificate and chain have been saved at:/etc/letsencrypt/live/console.postfix.io/fullchain.pem
Your key file has been saved at:/etc/letsencrypt/live/console.postfix.io/privkey.pem…
Edit main.cf vim /etc/postfix/main.cf
Replace the following lines : smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil…
article1tele.dk is an ISP from Denmark. As per the Postmaster guidelines, tele.dk mail servers do not accept more than 3 messages per connection, if you attempt to send more emails, you would get the following error message :421 4.5.1 No more messages on this connection, see http://tele.dk/25153
The following quick How-to explains, how to configure Postfix to limit number of messages per smtp connection / session to danish domains which are hosted by tele.dk.Note: The following configurations worked on Postfix 3.2.3.Add the following to /etc/postfix/main.cf# mail.dk transport
transport_maps = hash:/etc/postfix/transport
teledk_initial_destination_concurrency = 3
teledk_destination_concurrency_limit = 3
Add the following to /etc/postfix/transport.mail.dk teledk:
You can add more domains by reviewing logs. These are some of common do…