Real case: a supplier always lands in quarantine

When it is not a coincidence

The workshop's ironmonger writes twice a week. Every other time, the message is held, with the reason "sender not authenticated". Farida is starting to find it tiresome.

What that reason means, precisely

The server sending those messages is not declared as allowed to write on behalf of that supplier. It is not an accusation: it is almost always an incomplete configuration on their side, very common in small firms. The Bouclier cannot guess it is an oversight rather than an impersonation — so it does what it must, and sets the message aside.

The right move

Add that sender to your always accepted senders, on the "My senders" screen. Their messages will now go through without examination.

Add the exact address of your contact, not the whole domain: if the domain is poorly protected, someone can impersonate it, and you do not want to have opened the door to the impersonator along with the supplier.

And do the supplier a favour

Tell them about it: their messages are probably landing in quarantine at all their customers, not just yours. Their IT provider will fix it in half an hour. It is a call that saves everyone time, and it puts you in a good light.