I think you all are facing problem of lead/helpdesk. As its not created automatically mail.
You have configured your mail server correctly action to create lead correctly set but still all
mail are not fectched or all mails are not create lead/helpdesk right ?
Some mails create messages instead of new lead ?
So, there may be chances you have configured mail server thats silently broken.
So, avoid this kind of stuff you can just check your mail server and check your aliases both are same , means here i give you example.
in your mail server : firstname.lastname@example.org for fetching incoming mail.
now in your users if there is similar 'nayi.pinakin' than its create problem.
So, check your aliases and be sure there is fetch mail server and user are not same.