As I've been migrating my network from one ISP to the other, in tiny steps, mistakes happen. I missed one line in my e-mail server configuration, so no e-mail for a while.

I think I'm still inside the retry interval for most legit mail servers, so that's a good thing.

As I transitioned the server hosting my mail server from its old subnet to the new one, I disabled the network interface the old one was using. Technically it's still "on," but it no longer is assigned an IP address.

I had run through the mail server's configuration files and fixed all the places I knew the address was used, and replaced them with the new one. I restarted the mail server, and saw successful incoming e-mail on the new IPs! I considered it a small success and wandered away.

Over the weekend I noticed a number of the things I'd normally see on my phone hadn't arrived. So this morning I took one more peek.

In a minor face-palm moment, after a quick ack command for the old IP address, I found the one line in a configuration file I'd missed. It was the one that bound the outbound SMTP server, so the e-mail would come from the same address that my DNS security bits say it would come from. That put all of the forwarded mail, like those I expected to see on my phone, in the queue to be sent later.

I corrected that address entry, restarted the mail server, and a bevy of outbound messages filled the logs. I've got a rate limiter on the server, so it'll take a few minutes for the message to go out, but almost instantly my phone pinged with a delayed message.