I've been using Gandi's free mailboxes since 2019 when I de-Googled, they provide easy setup for SPF/DKIM/DMARC. Not sure about the other two. No significant deliverability issues to report. They offer IMAP and a choice between two web UIs which is all I need.

I'd be more than happy to pay for their service in general, just not under duress. If they'd have given me 6 months to onboard I'd have been perfectly fine with $3/mo for email. If I'm going to be abused with a false sense of urgency and pushed to make a quick decision, I'll just leave.

As a bundled service it was fine, I have a complete copy of my emails on my client(s) anyway so what it really did was give an IMAP interface to use for sending and receiving emails under my domain that dealt with the entire "Google et el are pretty evil about personal email boxes".

Its not worth £3 a month per box when previously the Gandi markup was £4 a year or so for the extra services on top of the raw domain price.