Yes literally it threw an invoice from AWS into spam recently. Regularly throws financial docs into spam. Like you, i have a problem with false positives not false negatives.

I brought it up with support once and the domain was failing DMARC. Headers from the AWS email that has a spam score of 9.1! I don’t know much about email but something must be wrong there on Fastmails side.

x-sieve: CMU Sieve 3.0

X-Spam-known-sender: no

X-Spam-sender-reputation: 500 (none)

X-Spam-score: 9.1

X-Spam-hits: DCC_CHECK 1.1, HEADER_FROM_DIFFERENT_DOMAINS 0.249, HTML_MESSAGE 0.001, ME_SENDERREP_NEUTRAL 0.001, MIME_HTML_ONLY 0.1, MPART_ALT_DIFF 0.724, RCVD_IN_DNSWL_NONE -0.0001, RCVD_IN_MSPIKE_H4 0.001, RCVD_IN_MSPIKE_WL 0.001, SPF_HELO_NONE 0.001, SPF_PASS -0.001, T_REMOTE_IMAGE 0.01, URIBL_DBL_ABUSE_PHISH 7, LANGUAGES en, BAYES_USED none, SA_VERSION 4.0.1

X-Spam-source: IP='54.240.9.110', Host='a9-110.smtp-out.amazonses.com', Country='US', FromHeader='com', MailFrom='com'

X-Spam-charsets: subject='UTF-8', html='UTF-8'

I disagree. Their spam filtering has been top notch for me. Sometimes spam does get through, but marking that as spam has made sure the next ones of the same are flagged correctly.

Lately LLM generated spam has fooled it more often, though. Let's see if that becomes a problem.

It's not. I wrote about this a couple times. Here's how it works: the personal spam filter kicks in after having trained on ~100-200 spam emails. You need to mark them as spam (you might want to use a filter initially if they all have a common pattern) and delete them regularly from the spam folder. Spam training kicks in only when you a spam message is deleted (to avoid training on false positives)

I went through the same phase when I first moved to Fastmail, and this is what customer support explained after some back-and-forth. I don't have spam in my Inbox any more (despite receiving ~20 spam emails per day)

I agree. Their spam filtering is absolute trash. I get 3-4 spam messages a day in my inbox. I file support tickets for it and they always tell me there is nothing they can do.

That's not exactly a reason to stick with gmail. Gmail will mark anything as spam.