Why didn’t the person I wrote to get my message?
Most of the time, the message did go out but is waiting at the other person’s end, in their junk mail.
Step by step
In Mail, open the Envoyés (Sent) folder: if the message is there, it did go out.
Open it and check the address on the À (To) line, letter by letter.
Ask the other person to look in their junk folder (or “spam”).
Still nothing? Report it, giving the address and the time it was sent: we’ll trace its path.