Looking for a spam solution, currently running Domino 12.0.2, planning on upgrading in the new few months, running Domino on IBM Series I system.
Wondering what others are using for spam/email filter, if you wouldn’t mind sharing?
Am currently using my firewall vendors quarantine server, but it is going away as an option, so I have to find a replacement asap 
Thanks for any ideas!
There are several options:
Trend Micro Vision One Cloud Email Gateway Protection (Cloud based)
Trend Micro Deep Discovery Email Inspector (On-prem, Physical and Virtual Appliance)
Fortinet FortiMail (Cloud-based, On-prem, Physical and Virtual Appliance)
Proofpoint (Cloud based)
And may others.
If looking for community supported:
SpamAssasssin
ProxMox Mail Gateway
MailScanner
Hope this helps.
Best,
Elvis
Mimecast if very good and at the high end of cost. Proofpoint is good also.
I recently started using https://mailroute.net/. Much better price. Fewer buzzes and whistles, but is has the standard features and you can also subscribe to their high-availability (web mail on their servers that users can get to if your mail server is down).
There is Securence, too. It is a SaaS so there is nothing to host on-site, we route our MX through them. They bill by the user, so for smaller companies, it is a pretty inexpensive option. They have a responsive tech support so a handful of our clients have really loved them.
Our company Mindwatering can also sell an account if you like. There is also eFa, but they just had a transition a few months ago to new maintainers, so we are watching how the new one bakes out. That said the project is open source and you can install via the git repo. A bunch of our clients are using that one. We also have a client using mimecast, and overall they are happy, too.
You can use MIB (MailIn Black): https://www.mailinblack.com/