When trying to send an email to mailing lists the message appears to be sending two times. The first time it sends successful but the second time does not. When the message is sent the first time it uses the correct "MAIL FROM" command but the second time it just uses "FROM". This causes a "error 500 unrecognized command" and the session eventually closes.The sender gets a message that the their message could not be delivered even though it was delivered successfully the first time. Here are logs showing what is happening.

[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] rsp: 220 mailserver.domainname.net
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] connected at 10/22/2014 11:34:51 AM
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] cmd: EHLO FAMREC1417
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] rsp: 250-mailserver.domainname.net Hello [xxx.xxx.xxx.xxx]250-SIZE 31457280250-AUTH LOGIN CRAM-MD5250 OK
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] cmd: AUTH LOGIN
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] rsp: 334 VXNlcm5hbWU6
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] Authenticating as sender@domainname.net
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] rsp: 334 UGFzc3dvcmQ6
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] rsp: 235 Authentication successful
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] Authenticated as sender@domainname.net
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] cmd: MAIL FROM: <sender@domainname.net>
[2014.10.22] 11:34:51 [xxx.xxx.xxx.xxx][21275780] rsp: 250 OK <sender@domainname.net> Sender ok
[2014.10.22] 11:34:52 [xxx.xxx.xxx.xxx][21275780] cmd: RCPT TO: <mailinglistdomainname.net>
[2014.10.22] 11:34:52 [xxx.xxx.xxx.xxx][21275780] rsp: 250 OK <mailinglistdomainname.net> Recipient ok
[2014.10.22] 11:34:52 [xxx.xxx.xxx.xxx][21275780] cmd: NOOP
[2014.10.22] 11:34:52 [xxx.xxx.xxx.xxx][21275780] rsp: 250 OK
[2014.10.22] 11:34:53 [xxx.xxx.xxx.xxx][21275780] cmd: DATA
[2014.10.22] 11:34:53 [xxx.xxx.xxx.xxx][21275780] rsp: 354 Start mail input; end with <CRLF>.<CRLF>
[2014.10.22] 11:36:25 [xxx.xxx.xxx.xxx][21275780] rsp: 250 OK
[2014.10.22] 11:36:25 [xxx.xxx.xxx.xxx][21275780] Data transfer succeeded, writing mail to 196131677.eml
[2014.10.22] 11:36:26 [xxx.xxx.xxx.xxx][21275780] cmd: MAIL FROM: <sender@domainname.net>
[2014.10.22] 11:36:26 [xxx.xxx.xxx.xxx][21275780] rsp: 250 OK <sender@domainname.net> Sender ok
[2014.10.22] 11:36:26 [xxx.xxx.xxx.xxx][21275780] cmd: RCPT TO: <mailinglistdomainname.net>
[2014.10.22] 11:36:26 [xxx.xxx.xxx.xxx][21275780] rsp: 250 OK <mailinglistdomainname.net> Recipient ok
[2014.10.22] 11:36:26 [xxx.xxx.xxx.xxx][21275780] cmd: NOOP
[2014.10.22] 11:36:27 [xxx.xxx.xxx.xxx][21275780] rsp: 250 OK
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: From: "Sender Name" <sender@domainname.net>
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 500 command unrecognized
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: To: <mailinglistdomainname.net>
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 500 command unrecognized
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: References: <7D267661419E6741A0E77D9E16C73FA28D6B3E09@SOCEMMB02>
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 500 command unrecognized
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: In-Reply-To: <7D267661419E6741A0E77D9E16C73FA28D6B3E09@SOCEMMB02>
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 500 command unrecognized
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: Subject: FW: Ohio SPF SIG Photo
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 500 command unrecognized
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: Date: Wed, 22 Oct 2014 11:36:09 -0400
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 500 command unrecognized
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: Message-ID: <00c001cfee0d$f28cc110$d7a64330$@domainname.net>
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 500 command unrecognized
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] cmd: MIME-Version: 1.0
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] Closing transmission channel: too many bad commands
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] rsp: 421 Too many bad commands, closing transmission channel
[2014.10.22] 11:37:15 [xxx.xxx.xxx.xxx][21275780] disconnected at 10/22/2014 11:37:15 AM