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Apparently I installed that thing in 2006 and I last updated it in 2016, then I quit updating it for some reason that I totally forgot. Probably laziness...
It's been running for quite some time and we kind of forgot about it in the closet, until the SSH tunnel we use to get our mail outside our home stopped working because modern openssh clients refuse to use the antiquated key cipher I setup client machines with way back when any longer.
I just generated new keys with a more modern cipher that it understands (ecdsa-sha2-nistp256) and left it running. Because why not 🙂
Unfortunately that's not true. I've been running mail servers under my domain since around 2000, almost as long as Microsoft has been running Hotmail, and I was certainly following good standards like SPF and DKIM well before they considered such a thing... and yet Microsoft is the bane of my mail server's existence. Despite no compromises resulting in spam blasts, MS still regularly shuts me out with no reason given and no hits showing on their monitors. If I can find their email address to ask what the problem is, I get a generic "your domain has been cleared" sort of reply but never any reason why they blocked me in the first place.
Do you have a "spammy" TLD?
My primary domain is something that people have blacklisted because four letters happen to partially match a word that could be spammy (how ridiculous is that?), however the mail servers (the ones they keep blocking) are attached to my computer business name which I registered in 2006, so there's really no reason why they should block it for that reason.
To be far you didn't update for almost a decade. The large email provides fear you