Where did the letter go to spam or not?

Question

Email

Wherever the letter got into spam or not, I send it from my server. I saw somewhere that mailers can send a postback in case of spam.

Answer 1

Can send
May not send
May give away the status
May not give back
Can give the status that it has been delivered (to be left behind), but not delivered
Can give the status that the user does not exist (to be left behind), but deliver the letter
Everything depends entirely on the imagination of the admins.