unable to attach a file in erpmail

[madhuarepalli]

i am unable to attach a file in erp mail. It show error message like....

The following file has not been received
Filename query.txt
Size 347 bytes
Reason File Type Not Allowed
Tip: Try uploading a file with another extension.

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In this scenario how to attach a file in erpmail. i tried some formats like .xls,.txt,.pdf,.doc,.html..........

Kindly help me in this situation.