I am also now seeing this in the email server logs:
10:56:03 [10.0.0.1][9175607] cmd: EHLO BigBox1
10:56:03 [10.0.0.1][9175607] rsp: 250-mail.inaboxdev.com Hello [10.0.0.1]250-SIZE 5242880250-AUTH LOGIN CRAM-MD5250 OK
10:56:45 [10.0.0.1][9175607] cmd: MAIL FROM:<robert@inaboxtech.com>
10:56:45 [10.0.0.1][9175607] rsp: 250 OK <robert@inaboxtech.com> Sender ok
10:56:45 [10.0.0.1][9175607] cmd: RCPT TO:<robert@inaboxtech.com>
10:56:45 [10.0.0.1][9175607] rsp: 250 OK <robert@inaboxtech.com> Recipient ok
10:56:45 [10.0.0.1][9175607] cmd: DATA
10:56:45 [10.0.0.1][9175607] rsp: 354 Start mail input; end with <CRLF>.<CRLF>
10:57:06 [10.0.0.1][9175607] data transfer failed.
10:57:06 [10.0.0.1][9175607] disconnected at 7/22/2013 10:57:06 AM