This does not help a lot.
The only thing positive is that I have the correct translation of the file I referred to.
It's WINDOW/PREVIOUS RECIPIENT.
In fact what happens is that the few recipients that are there cannot be removed and that NO NEW RECPIENT are entered either if I send or recieve mails.
I do not know when this probleme started but what is clear is that some "week" ago it was working fine.
The only thing that comes to mind is that as you are on 10.6.8 and the combo update for that OS is known to have put right minor corruptions in Mail, you might consider downloading ... Mac OS X 10.6.8 Update Combo. and applying it.
It won't do any harm applied over the top of any previous download. When it is finished restart your computer. As I said, it won't do any harm but neither can I be sure if it will solve the problem.
I will do but I do not believe it will help for two reasons:
1. I have two other computers running with 10.6.8 and mail is working fine.
2. On this particular computer I checked my wife's account and mail is OK too.
Therefore I believe that there is a file corrupted on my own account and it is not a general "mail" problem. But I do not know how to locate it and / or remove / replace it.
I'll keep you posted.
The installation of 10.6.8 Combo did not improve anythings.
I read in one forum that the Previous recipient file was in fact located in adresbook file.
I recovered (thanks to my timemachine safeguard) the file at a date (some weeks ago) that I believed was OK.
I copy it in today files and fortunatley it worked.
I beleieved I replaced the corrupted "MailRecents-v4.abcdmr" file by a valid one.
For the mment it's OK
Thanks to all for your help.