I doubt the number of US military who legitimately needs to email .ml addresses is that big. Block it for everyone minus known ppl who deal with mali stuff (and have been briefed on the issue). Sort out the ones you missed on day 0. Worst case some legitimate mail to mali gets delayed - whatever. If its urgent, i hope they have better comms channels than email. For external contractors, send them an email with vage threats of consequences if they leak (and instructions to fix their address books). Some mail will still be missent, but this should mitigate most of it.