I'm trying to use the out of the box method of using a data extension created with the Domain Exclusion Data Extension Template, and (surprise, surprise) it's throwing an unspecified error when I try to send the email.
For no particular reason, I suspect the cause is that I'm trying to use the Domain Exclusion functionality in conjunction with other exclusion scripts. So, I'm going to try using a regular exclusion expression that performs a lookup against the Domain Exclusion Data Extension.
And since I didn't find this anywhere else on StackExchange... and I'd already written it... thought I might as well share. Here's what I wrote:
(If it works for you, appreciate an up-vote. I'm a noob, and can use the points.)