Hi havacuban,
It seems that you have issue with the special mail user of your Domain Controller. Did you do anything to this user?
Aparently, you have at least two errors:
One error is: 'The request is a bind request to a user account that has been locked'. You can do the following to try to solve this error:
1. Check the name of the user.
samba-tool user list | grep 'zentyal-mail-'
{/code]
2. Check if the user is locked:
[code]
ldbedit -Lv -u name_of_the_user | grep 'Account Flags'
NOTE: If it has the flag 'D' it means that it disabled
2.1 To unlock the user:
samba-tool user enable name_of_the_user
3. Restart the mail module and check if the error have disappeared.
And the other error is: 'he password fails to meet the criteria the server is configured to check'. Do you remember if you change his password? Please, take a look at the file '/var/lib/zentyal/conf/zentyal-mail-your_user_name.passwd' and check if the file was changed recently. In case it doesn't, you could try to set the same password to the user and restart again the Mail module.
smbpasswd name_of_the_user
Hope it helps.
Best regards, Daniel Joven.