[FIX] mail: ensure case insensitive check when (de)activating blacklist records

Now that blacklist records are set as lower case be sure all checks in
blacklist are done accordingly by using the sanitizer before comparing
email adresses.

This commit is related to task ID 33224 (original blacklist implementation
done for v12) and its PR #25966 as well as task ID 1889703 (tests and fixes)
and its PR #27330. Done with collaboration of @dbeguin.

addons/mail/models/mail_blacklist.py

@@ -59,7 +59,8 @@ class MailBlackList(models.Model):
         return super(MailBlackList, self).write(values)
 
     def _add(self, email):
-        record = self.env["mail.blacklist"].with_context(active_test=False).search([('email', '=', email)])
+        sanitized = self._sanitize_email(email)
+        record = self.env["mail.blacklist"].with_context(active_test=False).search([('email', '=', sanitized)])
         if len(record) > 0:
             record.write({'active': True})
         else:
@@ -67,7 +68,8 @@ class MailBlackList(models.Model):
         return record
 
     def _remove(self, email):
-        record = self.env["mail.blacklist"].with_context(active_test=False).search([('email', '=', email)])
+        sanitized = self._sanitize_email(email)
+        record = self.env["mail.blacklist"].with_context(active_test=False).search([('email', '=', sanitized)])
         if len(record) > 0:
             record.write({'active': False})
         else: