[2.3.0] Checkmk Werk 16495 created: check_mailboxes: fix check of multiple mailboxes

[//]: # (werk v2) # check_mailboxes: fix check of multiple mailboxes key | value ---------- | --- date | 2024-03-04T13:04:06+00:00 version | 2.3.0b1 class | fix edition | cre component | checks level | 1 compatible | yes When selecting to check multiple mailboxes, the software always checked only the last specified mailbox. This werk fixes this behaviour.