TODO

This probably isn't supported. Login via SSH and use apt to update the system.

After the update, postfix won't start anymore. It shows the following error message:

Apr 10 18:17:46 pmg postmulti[961]: fatal: file /etc/postfix/main.cf: parameter myhostname: bad parameter value: pmg.int.example.com.

Edit the main.cf file of postfix.

vi /etc/postfix/main.cf

There are lines similar to the following two.

mydomain = int.example.com.
myhostname = pmg.int.example.com.

Remove the . (dot) at the end of both configuration options.

mydomain = int.example.com
myhostname = pmg.int.example.com

Start postfix again.

systemctl start postfix