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Best email provider against spam?
(lemy.lol)
This is a most excellent place for technology news and articles.
You can look for a service that provides a mail security gateway, or host your own. My personal solution is mimedefang milter on sendmail which will blow away any canned solution you will find. But you have to know what you are doing with it.
There is barracuda, but they are $$. Another option is proxmox mail gateway. Not as fast as mimedefang, but it has a nice gui.
https://www.proxmox.com/en/proxmox-mail-gateway/overview