CRM 2011 On-Premise: CRM Queue not working

Hello

I have a CRM 2011 on-premise system and there are 3 queues in it. There is a CRM workflow which fires from queue item and creates CRM cases back of it. All 3 queues are setup exactly the same and are from same domain. 

2 queues work as expected and workflow fires normally. The last queue is not working when an email is sent to that queue's email address. 

Checks done:

- Queue record - Given correct username and password. And Approved email

- CRM Email Configuration: Incoming emails are set correctly

- Checked with network team: looks like emails are received in CRM server but for some reason it is not hitting CRM.

Could anyone help me on this please?

Thanks

AB