IsabelSatimis:
Best regards = Muchos saludos.
For the rest, it's ok. It mustn't doesn't have to be perfect, must does it? They know you aren't fluent in Spanish..
Merry Christmas to you!
I.
I know this is a Spanish forum but... I think we are here to learn from each other...
So, I take a chance to make a slight correction and post a clarification note.
must not means that you deny or forbid to do something
e.g. You musn't do it. - You say when you want to tell someone that he or she is not allowed to do it (You or someone/something else does not let to do it.)
Cheers.
And...
¡Feliz Navidad a todos!