SecurenceMail

Pros: Works extremely well.
Once set up, adding/maintaining users/domains is not difficult.
Phone support is available 24x7. I actually need to contact support very rarely.
Integrates very well with Microsoft 365 Exchange/Outlook.
There has only been one notable service outage in several years, and it did not last long. I have no issues with this.
If I had to do it all over again, I would not hesitate to go with this vendor.

Cons: UX is a little bit confusing, but to be fair, this is a complex product by its nature. This gets better with use.

Overall: I'm an MSP. I am not just happy with Securence - I'm thrilled with it. I'm managing about 100 users now with about a dozen domain names.

All users have Securence filtering. All Microsoft 365 users have implemented archiving, and the majority also have email continuity enabled.

Most users are on Microsoft 365; Securence has a partnership arrangement with Microsoft, so they are relatively simple to insert into the mail flow chain.

Another dozen or so users are using Securence as their email server, typically using Thunderbird and/or their default mobile email client. Securence webmail is OK, but folks seem to prefer Thunderbird.

After the modest learning curve, it's been great. Yes of course there are some bad emails that slip through, as there are with all filters. But the amount of false-positives is astoundingly close to zero. And they wrap a filtering URL around links embedded in emails, as further protection.

I've implemented DKIM, SPF and DMARC for all domains, and this is working fine as well.

Securence support is also very good. I can call support 24 x 7 and usually get someone on the line quickly. Happily, this is not needed very often.

It's as set-and-forget as I've ever seen for a product such as this. I like easy!