I have many returning false positive blocked mails from an organization partner, that always blocked their reply on our emails. Our quarantined report says Blocked by organization policy : Antimalware policy block by file type
The only attachment in the mail was an image in signature. The signature was ours, but when they answare the mail the incoming reply massage always blocked with the reason above.
I have two question:
How can I be sure what file is the wrong tpye that Defender needs to block?
How can be bypass that our reply massage never be blocked (without removing signature pics)?
The HTML code of this mail's signature:
<span style="font-size: 8.0pt;line-height: 120.0%;color: rgb(31,73,125);"><img border="0" width="225" height="45" style="width: 2.3472in;height: 0.4722in;" src="cid:**91e91ec32e9dc19a9bfcf381ec58f4955ad568c1867371b55da.mpf**"></span>
I do not know how can it be .mpf extension in their reply. We use .jpg or .png in signatures. I've already checked anti-malware policies file types and .mpf is not on the black list.
