Emails look like spam to some spam software

[bullfrog]

My emails look like spam to some spam detection software. They are not spam. The problem appears to be coming from this line in the email header:

Received: from jbx241yz (failure[71.194.179.15])
by comcast.net (rwcrmhc12) with SMTP

jbx241yz is the name of my computer. I am using a Comcast cable modem to a NETGEAR wireless router to my desktop Gateway computer. NETGEAR says it is not caused by them. Comcast says it is not caused by them. My email ISP server had whitelisted me so my email can get delivered within their system. I am part-time university faculty and one of my students is getting a spam flag on my emails.

The NETGEAR guy said there must be client-server software running on my computer. I can't see what it might be. I was using McAfee virus and firewall. Gave it up for AVG. That changed the header to what you see now. With McAfee, after jbx241yz it said "Server unknown"

Any help is much appreciated.