Illegal mix of collations in OTRS

The problem is described [ here], but not really the solution. I was having it on fetching some emails into otrs. Incidentally, the mail stayed into the mailbox (since the insertion into otrs database could not occur), and it was fetched again and again, filling the anti-spam proxy between the mailbox and otrs. This is what alerted me. Actually the solution is [,6528,225042#msg-225042 here]. I performed the alter table on the `article`table, and everything went into order.