PMG with O365

I don't have any experience with o365 - but I would assume it's possible - see e.g.:
https://forum.proxmox.com/threads/mail-gateway-routing-solution.117129/#post-506799
and
https://pmg.proxmox.com/wiki/index....ox_Mail_Gateway#Configuring_Outbound_Scanning

You just need to:
* configure your O365 to send outbound mail to PMG's port 26 (or what you've configured as your internal port)
* configure PMG to send mails for your domain to your O365 (and allow PMG's IP there)
* set the MX record of your domain to point to PMG

I hope this helps!