Email statements blocked by Google

When we email statements from the new interface to clients who use Gmail or Google Apps, the messages are being returned with the following error. Statements can be sent successfully using the old interface.

This is a MIME-encapsulated message

--s1SHYnp2027603.1393608889/resolver2.sv4.zoho.com

The original message was received at Fri, 28 Feb 2014 09:34:45 -0800

from [172.29.253.193]

----- The following addresses had permanent fatal errors -----

<[RECIPIENT ADDRESS]>

(reason: 552-5.7.0 This message was blocked because its content presents a potential)

<[CC TO US]>

(reason: 552-5.7.0 This message was blocked because its content presents a potential)

----- Transcript of session follows -----

... while talking to aspmx.l.google.com.:

DATA

<<< 451-4.3.0 Multiple destination domains per transaction is unsupported. Please

<<< 451 4.3.0 try again. yo5si2794320pab.34 - gsmtp

<[RECIPIENT ADDRESS]>... Deferred: 451-4.3.0 Multiple destination domains per transaction is unsupported. Please

<<< 552-5.7.0 This message was blocked because its content presents a potential

<<< 552-5.7.0 security issue. Please visit http://support.google.com/mail/bin/answe

<<< 552-5.7.0 r.py?answer=6590 to review our message content and attachment content

<<< 552 5.7.0 guidelines. yo5si2794320pab.34 - gsmtp

554 5.0.0 Service unavailable

... while talking to alt1.aspmx.l.google.com.:

DATA

<<< 552-5.7.0 This message was blocked because its content presents a potential

<<< 552-5.7.0 security issue. Please visit http://support.google.com/mail/bin/answe

<<< 552-5.7.0 r.py?answer=6590 to review our message content and attachment content

<<< 552 5.7.0 guidelines. r4si12154093icw.114 - gsmtp

554 5.0.0 Service unavailable