If you changed the hostname/FQDN of a Linux server, you may end up with some issues, especially with mailing if some areas were forgotten with that change. Here is a quick procedure involving all the steps you should be looking for. (The following example is based on a Debian Linux system running Postfix MTA.)
1. Update the hostname file :
/etc/hostname
2. Update the hosts file :
/etc/hosts
3. Update the mailname file :
/etc/mailname
4. Update the Postfix main.cf file :
/etc/postfix/main.cf
myhostname =
mydestination =
5. Update the DNS pointer record (PTR), if you had any :
0.0.0.0.in-addr.arpa. IN PTR your-new-hostname.domain.tld
OPTIONAL
6. Update the aliases file if you had any added entries with the previous FQDN
/etc/aliases
6.1. Rebuild the aliases database :
newaliases