[69_years_and]

To add to the fray: https://yunohost.org/ is an option too for easy install and setup of a mail server - there was a recent HN item on them a while back. Been using it for a month or two and it's worked great so far. Needs Debian. Supports multiple domains.

[csixty4]

I keep forgetting Yunohost can do that. Is there a guide to setting up email services?

[hrjet]

I had good experience with Citadel for an internal mail solution. It's a little old fashioned, but good enough for our needs. The setup was especially easy with the default ubuntu packages.

[ausjke]

I'm also testing citadel for a small team, the issue is that I can't get thunderbird/lightning to sync the calendar with citadel, email works fine, will be checking kolab soon

[hrjet]

Just FYI, we are not using the calendaring system from Citadel; so can't give any report for that.