Hi and txs for the follow-up. Very kind of you.
It is 8 bit and UTF8 (which were the standard settings)
I have made further tests for you 🙂
With this message the test email keeps spinning :
essai avec accent é ()
et deux lignes
With the following it works immediately
essai avec accent é () et une ligne
So obviously the issue would be when you have multiples lines ("ENTER" with the keyboard).