Choosing the right email service vendor

I’ve been trying to research what email services would work best for LXC containers, but all I can find is docker/lxc comparisons, and just general information about email vendors.

I’m trying to choose the email service vendor that would work best for our network’s LXC Email container (for Centos 7). Any suggestions?

You can choose whatever e-mail daemon / service you want, are you looking for something specific ?

Is that also related to your capstone homework (mentioned in the other thread)?
If you really need an email service vendor, you can use any that supports Linux.
There are no LXD-specific issues (or LXC) here because you do not need to get your host to listen to the SMTP/POP3/IMAP ports; these are handled by the vendor.