Legit Emails are going to QUIT

2015-10-21 08:54:02 H=zeus.email-sent.net [66.241.99.248]:2594 Warning: Sender rate 1.0 / 1h 2015-10-21 08:54:02 H=zeus.email-sent.net [66.241.99.248]:26166 Warning: Sender rate 2.0 / 1h 2015-10-21 08:54:23 1ZosuN-0004PM-2s <= NEWFAX@faxtoyouremail.com H=zeus.email-sent.net [66.241.99.248]:2594 P=esmtps X=TLSv1:DHE-RSA-AES256-SHA:256 CV=no S=5978 id=20151021125341.985046.1912355632.swift@zeus.email-sent.net T="NEW FAX (1 page) - 10-21-2015 at 06:53:01 AM MST" for b@domain.tld 2015-10-21 08:54:23 1ZosuN-0004PL-2t <= NEWFAX@faxtoyouremail.com H=zeus.email-sent.net [66.241.99.248]:26166 P=esmtps X=TLSv1:DHE-RSA-AES256-SHA:256 CV=no S=5984 id=20151021125340.985046.261907014.swift@zeus.email-sent.net T="NEW FAX (1 page) - 10-21-2015 at 06:53:01 AM MST" for t@domain.tld 2015-10-21 08:54:23 SMTP connection from zeus.email-sent.net [66.241.99.248]:2594 closed by QUIT 2015-10-21 08:54:23 SMTP connection from zeus.email-sent.net [66.241.99.248]:26166 closed by QUIT I am trying to fix why these e-mails are not showing up in the user's mailboxes. IS this a filtering issue or more a DNS lookup issue? I've tried whitelisting the IP with IP addresses exempt from all SMTP sender, recipient, spam, and relaying checks. IP addresses you enter here are stored in /etc/skipsmtpcheckhosts. These senders must still use an RFC-compliant HELO name if the Require RFC-compliant HELO setting is enabled. I have also tried doing nslookups and all checks out. Even other incoming mail works just fine. I am not sure why this one is being dropped.