Unable to create ticket by email/maileater

Document ID : KB000093289
Last Modified Date : 03/05/2018
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Tickets create by email/maileater does not work. It can happen after recent fail-over of background server between standby server.

In SDM 17.1 maileater_nxd.log recorded: 
2018-04-16 20:19:11:998 ERROR [ForkJoinPool-1-worker-0] c.c.S.m.ConnectSession - [mailbox:Service Desk Manager:400001] Error processing email from: localhost:1110  (1110 is the Port Override in mailbox setting)
java.lang.StringIndexOutOfBoundsException: String index out of range: 0 
When the "Filter String/Rule" against the Mailboxes have no contents or blank, this causes the error in stdlog and unable to create tickets via maileater. 
Mail rule Empty Filter

Once the mailbox rules has proper value in "Filter String/Rule", tickets can create by email.

Below is out of box Default mailbox rules has non-blank Filter String.
User-added image