Because why not 🙂

Because security.

Good thing there hasn't been any remotely exploitable security bugs in any of the mail system components in the 6 years since Debian 7 went EoL

That was a good test run. I think it's time to put it into production.

I'm fairly certain that SSH and whatever else you're exposing has had vulnerabilities fixed since then, especially if modern distros refuse to use the ssh key you were using, this screams of "we found something so critical here we don't want to touch it". If your server exposes anything in a standard port, e.g. SSH on 22, you probably should do a fresh install (although I would definitely not know how to rebuild a system I built almost 20 years ago).

That being said, it's amazing that an almost 20 year old system can work for almost 10 years without touching anything.

You send mail to Gmail and Hotmail and it's actually accepted? How?

Genuinely surprised when I see people running mail servers without issue. I suppose getting in relatively early means you're not immediately sent to junk mail lists by the big players.

Family email server? Your family have an email server to themselves? You managed to deal with block lists over 2 decades and more?

My utmost respect to your dedication

It's had a good run. Let the little guy have a rest. Whatever you replace it with will consume less electricity.

you name your servers with nuclear subs names?

I gave up running an email server long ago - I thought it was basically impossible because too many spammers were doing it for nefarious purposes.

Believe it or not I've come into contact with Microsoft Exchange 2010 running on Server 2008 for 2000 days once. The company had ransomware.

Please tell you to at least have Freexian patches installed...

Not to be that guy but why not use Curve25519?

I still remember all the conspiracies surrounding NIST and now 25519 is the default standard.

In 2013, interest began to increase considerably when it was discovered that the NSA had potentially implemented a backdoor into the P-256 curve based Dual_EC_DRBG algorithm.[11] While not directly related,[12] suspicious aspects of the NIST's P curve constants[13] led to concerns[14] that the NSA had chosen values that gave them an advantage in breaking the encryption.[15][16]

That's the power of Linux. It can work for decades without issues.

I hope you get your data off and then burn it and everything around it. It could be easily compromised you knowing. It could easily be used for spamming