This is your sendmail therapy thread. Relate how sendmail scarred you here. :-)
I use to be a Sendmail consultant.
I've seen things you people won't believe. Open SMTP relays with zero firewall protection. I've watched people use sendmail to get root without a password. I've seen volumes of email lost in time, like bits into /dev/null. Time to patch.
UUCP with qmail and later Postfix was a great way to shove e-mail over these really unreliable connections. The g protocol worked amazingly well over these unreliable connections because it could pick up where it left off, so as long as you could get a few packets through, eventually your (sometimes large) e-mail messages could make it through, even if they had the spend the night trying.
The company kept that architecture well into the 2010s, even when we all had fairly speedy, reliable Internet connections, because it just worked really well. They eventually went to gmail years after I left.
UUCP had it's issues, but it was (and still is) one of the best was to transfer stuff over really bad connections. We worked at a place where we had really remote locations and UUCP stuff worked without much work.
Plus, I learned a ton in writing something to do reports and monitoring of the UUCP connections. Fun times, but I am still scarred Sendmail. Some wounds are pretty deep.
I had recommended they switch to using Taylor UUCP, because it splits the queue directory up into a hierarchy. They said Taylor wasn't mature enough, but I asked Ian Lance Taylor about it and he laughed and said "<THE major commercial UUCP provider> doesn't seem to agree." :-)
I've always heard that Kermit has really great protocols for handling horribly, horribly bad modem connections. I had at times wondered if a kermit UUCP protocol would have been useful.
We did almost all sysadmin expertise in-house, but for this Sendmail, we brought in a consultant.
It was a name I recognized from Usenet, and knowingly meeting a "famous" person was pretty new to me at the time. Turns out he wasn't a Unix graybeard (closer to my young skinny nerd age), and he was working on a Neuroscience PhD, while building/fixing everyone's Sendmail setups.
I didn't know to ask him which discipline was more difficult.
1. https://www.linusakesson.net/programming/sendmail/index.php
I run to the nearest Internet cafe and discovered they're blocking SSH ports. It took quite some time to unblock it, make the changes (it took less than a minute) and pray nobody intercepted my access data and make a mess before I get back. I've never felt so ashamed about my lack of professionalism in my entire life. I literally hated myself for being forced to use a public Internet cafe to configure my server.
https://www.mit.edu/people/eichin/virus/strategies.html:
“Debugging mode has many features, including the ability to send a mail message with a program as the recipient (i.e. the program would run, with all of its input coming from the body of the message).“
I don’t know why that page follows that with “This is inappropriate” /s
Ok, I may be lying, but if the sheer mass of that book was more than sufficient to convince me to never try configuring sendmail.
Or the pain of somebody on the team routinely editing the output files without making the changes on the config files, and never knowing whether it'll work the same when you're done.
I worked in a very Make oriented place. If you need to do any processing on files, which not only includes compiling them, but also pushing them to other servers, and loading them into memory on those servers, that should be done with Make. Because Make makes things :)
Now I'd rather write a Makefile than use whatever language's builder of the week. Make can make things, why do I need anything else?