As described in T248126: Please decom reading-wmf mailing list this is a request for a process enhancement to delete email addresses with privileged domain names (e.g., @wikimedia.org) from mailman at offboarding. This would reduce the odds of account compromise and otherwise misuse on the mailmain lists.

This probably ought to also apply to specific contractor work email addresses that aren't part of the set of well known privileged domain names, too, although that's potentially more complicated and harder to track - the task submitter isn't sure if that's an issue at present.

There may be complementary actions like resetting the list administrator password if the user was also an administrator of a list, although that's even more complicated process wise, perhaps.