Apparently, the email synchro was coded in such way that it never considered translations. It refers to a method of MetaModel which returns localized versions (as array values). This worked fine originally, as translations were missing. However, to be on the safe side, it should take the original allowed values (attribute codes) into account instead.
Since values of EmailReplica's "status" were translated, emails are marked as "Error".
Caused by https://github.com/jbostoen/itop-jb-mail-to-ticket-automation-v2/commit/28297709db08de247a4b38d5ebb22445ae1d01dc
Apparently, the email synchro was coded in such way that it never considered translations. It refers to a method of MetaModel which returns localized versions (as array values). This worked fine originally, as translations were missing. However, to be on the safe side, it should take the original allowed values (attribute codes) into account instead.