Hi
I am a system and network administrator, with more than 12 years of experience.
During that period I have installed, administrate and maintain a large number of various servers,
such as Web Server (Apache, IIS), Mail Server (Postfix, Exim, MS Exchange), DNS Server (BIND, Unbound, MS DNS), etc.
Based on, Ubuntu, CentOS, RHEL, etc.
Regarding the job, I'd like to clarify the following points: You mentioned skills and services necessary, however I'd like to ask you to be more specific about the very first work freelancer should do.
The fastest way or work is via direct SSH access, if you can grant it
As for the suggestion, Mailcow seems to be a good choice. It's an all in one dockerized solution based on postfix/dovecot. It will generate certificates using letsencrypt, and has a very nice admin panel. It is free and GDPR compliant.
Thank you for considering me for this job.
Have a good day,
Eduard