You might want to consider Rackspace, too:The timing on this thread is perfect. I am in the process of moving off of FastMail and onto G Suite, and I appreciate being able to learn from others' experiences. The primary reason I am doing this move is that I want to have centralized anti-malware and anti-phishing services on my email, and that is not available with FastMail, as far as I can tell.
I did a little searching at FastMail and elsewhere, looking for anti-virus options but didn't find any easy solutions. Here's what I did find:Rackspace said:Multi-layered Email Spam Filtering
... If mail passes the blocked email checks, we apply advanced content filtering to verify whether it is considered spam. Content filtering combines many techniques to analyze email structure and content, and create key indicators that identify patterns in email. These indicators are combined with industry-wide feedback from email providers across the internet about reported spam, phishing, and viruses. The end result is an accurate, adaptive, and evolving content filtering system that is highly effective at removing spam.
IETF said:RFC 5235 - Sieve Email Filtering: Spamtest and Virustest Extensions
The Sieve email filtering language "spamtest", "spamtestplus", and "virustest" extensions permit users to use simple, portable commands for spam and virus tests on email messages. Each extension provides a new test using matches against numeric "scores". It is the responsibility of the underlying Sieve implementation to do the actual checks that result in proper input to the tests.