BizTalk - Office365 Outlook Email Adapter not deleting mails

We've requirement that need to read the attachment from the e-mail and delete the e-mail once it's done.

But we're facing the issue in Office365 Outlook Email adapter. When using that adapter its behaviour is strange like it reads and delete(if email count is less). Sometimes reads and not deleting the mail(even if email count is less). Also, sometime it doesn't do anything.

We've installed CU3 update of BizTalk server then also we're facing the same issue.

Please check the properties we've set in the below image,

The payload is set to Deliver MIME.

Is there any specific software update to solve this?

Please guide us to solve this issue.