Some vendors can be really strict these days, outlook e.g. is especially strict. I dont know what vendor the government uses.
Usually one wouldnt expect gmail to be blocked as they are such a big player, but recently when I was in contact with CityFibre, their generic email address was blocking emails from gmail, but I was able to email staff directly fine so ended up having to do that. Thats the first occasion I have seen Gmail outright blocked, greylisting is better practice but its becoming more and more of a thing to just not deliver at all, not even to a spam box.
Also bear in mind its also not uncommon for organisations to close email inboxes, if staff member leaves or just to change it to something else (perhaps it became too publically known or something).
Edited by Chrysalis (Sun 12-May-24 10:44:04)