3 votesJoshua Bowden commented
If considered, please add it itsecurity@ not itsecuity@ !
1,517 votesJoshua Bowden commented
While I am an avid user of the '+' aliases along with a wildcard address (my own domain on Gmail) and would support a functionality like this, I've read the comments and have to agree with Troy's stance on this one, there are a number of good reasons why its not worth the investment.
Perhaps a simple solution is to do this on the user end - A simple program to read all the 'to' addresses with a '+' (or just every to field which reached the mailbox, which would support wildcard users) in them via Gmail API and then using HIBP API to check each of those addresses?