What do you use now?
Honestly, it's a huge relief. Self-hosting has gotten much more complicated over the years. It's very nice to know that there's a round-the-clock staff of professionals taking care of security, deliverability, and fighting spam. And software upgrades, of course!
I had this exact same problem 3ish years ago and bailed out to Fastmail for the same reason. The thing that made me throw in the towel completely was what I found out from someone who looked into it for me after I shook the tree of my professional and social contacts. This person was involved in Gmail but not directly in anti-spam, but told me that my domain had "limited reputation."
That domain, which predates the existence of Google by at least a year, had been hosted on the same IP address (IPv4 and IPv6) for almost a decade, with the same MX, A, and PTR records for the entire time. Nothing at all changed about how that domain was configured. Yet it was intermittently being flagged as "limited reputation" and either dumped in the spam folder or simply accepted for delivery and silently dropped.
I took that domain and moved it to Fastmail 3 years and 3 months ago--I know the exact date because I paid for three years of e-mail service at the time and recently renewed it--and haven't had a problem since because, unlike my single-server operation that used to be considered an equal peer on the Internet but not any more, Fastmail has enough pull and reputation to not have messages from its subscribers blocked by other e-mail hosts.
I don't think it's necessarily malicious in nature - more the product of spam filtering.
I wonder if email authentication methods like DKIM/SPF/etc.. help this problem these days.
It's been few years. I am on Mailbox's 12 Euro/year plan which has "forum" only support (I am not sure it changed after I became a customer). My emails suddenly stopped working once and I received email response after a week (which just had an irrelevant link). I had reset the mail setup by then after backing up email from local client. I replied to the email asking what went wrong and never received a reply. They seem very aloof and high-handed about customer support if I may say so.
I am looking at moving my mail provider. I have stopped using @mailbox.org mail for online a/c signups etc (which I did a lot earlier) and have started removing it from wherever it is used already.
Is Migadu stable and been around? How's their service and privacy track record? Did you evaluate any other provider in Euro 12-20/year budget range? My email usage is extremely low volume.
Their privacy policy is well written (I have read 100s if not thousands of them in grad school, I can tell you they’re not vague)
Support is human!!! It’s really good to know there’s a human on the other side.