FWIW .... here's the log from the mail server. This is a few transactions one successful "WebCAM" and the other fails ...
It almost looks like the EHLO greeting is sent improperly from the camera's new firmware.
*.172.65.* [0E6C] 10:42:10 Connected, local IP=192.168.1.2:587
*.172.65.* [0E6C] 10:42:10 >>> 220 mail.7900*.com ESMTP Mail Server @ 7900*.com; Thu, 17 Sep 2015 10:42:10 -0400
*.172.65.* [0E6C] 10:42:10 <<< EHLO WebCAM
*.172.65.* [0E6C] 10:42:10 >>> 250-mail.7900*.com Hello WebCAM [*.172.65.*], pleased to meet you.
250-ENHANCEDSTATUSCODES
250-SIZE 81788928
250-EXPN
250-ETRN
250-ATRN
250-DSN
250-CHECKPOINT
250-8BITMIME
250-AUTH PLAIN LOGIN DIGEST-MD5 CRAM-MD5 GSSAPI
250 HELP
*.172.65.* [0E6C] 10:42:10 <<< AUTH CRAM-MD5
*.172.65.* [0E6C] 10:42:10 >>> 334 PDIwMTUwOTE3MTA0MjEwQG1haWwuNzkwMG5vdmFkcml2ZS5jb20+
*.172.65.* [0E6C] 10:42:11 <<< bm9yZXBseSBhOTI1YjI4Njk4ODhmYTMxYzU4MDBiNDAzODRkNTk3Yw==
*.172.65.* [0E6C] 10:42:11 Authentication [SMTP] - Result=1, User=noreply@7900*.com, Method=2
*.172.65.* [0E6C] 10:42:11 >>> 235 2.0.0 Authentication successful
*.172.65.* [0E6C] 10:42:11 <<< MAIL FROM:<noreply@7900*.com>
*.172.65.* [0E6C] 10:42:11 >>> 250 2.1.0 <noreply@7900*.com>... Sender ok
*.172.65.* [0E6C] 10:42:11 <<< RCPT TO:<noreply@7900*.com>
*.172.65.* [0E6C] 10:42:11 >>> 250 2.1.5 <noreply@7900*.com>... Recipient ok
*.172.65.* [0E6C] 10:42:11 <<< DATA
*.172.65.* [0E6C] 10:42:11 >>> 354 Enter mail, end with "." on a line by itself
*.172.65.* [0E6C] 10:42:13 <<< 357866 bytes (overall data transfer speed=144417 B/s)
*.172.65.* [0E6C] 10:42:13 Start of mail processing
*.172.65.* [0E6C] 10:42:13 Message File Copy(<noreply@7900*.com> -> d:\Program Files\IceWarp\mail\7900*.com\noreply\ )
*.172.65.* [0E6C] 10:42:13 *** <noreply@7900*.com> <noreply@7900*.com> 1 357861 00:00:02 OK 201509171042110236
*.172.65.* [0E6C] 10:42:13 >>> 250 2.6.0 357861 bytes received in 00:00:02; Message id 201509171042110236 accepted for delivery
*.172.65.* [0E6C] 10:42:13 <<< QUIT
*.172.65.* [0E6C] 10:42:13 >>> 221 2.0.0 mail.7900*.com closing connection
*.172.65.* [0E6C] 10:42:13 Disconnected
*.172.65.* [0E6C] 11:11:01 Connected, local IP=192.168.1.2:587
*.172.65.* [0E6C] 11:11:01 >>> 220 mail.7900*.com ESMTP Mail Server @ 7900*.com; Thu, 17 Sep 2015 11:11:01 -0400
*.172.65.* [0E6C] 11:11:01 <<< EHLO smtp.txt
*.172.65.* [0E6C] 11:11:01 >>> 250-mail.7900*.com Hello smtp.txt [*.172.65.*], pleased to meet you.
250-ENHANCEDSTATUSCODES
250-SIZE 81788928
250-EXPN
250-ETRN
250-ATRN
250-DSN
250-CHECKPOINT
250-8BITMIME
250-AUTH PLAIN LOGIN DIGEST-MD5 CRAM-MD5 GSSAPI
250 HELP
*.172.65.* [0E6C] 11:11:01 <<< AUTH DIGEST-MD5
*.172.65.* [0E6C] 11:11:01 >>> 334 cmVhbG09Ijc5MDBub3ZhZHJpdmUuY29tIixub25jZT0iT0dZeU9UQTVNemc1TXpsaCIscW9wPSJhdXRoIixhbGdvcml0aG09bWQ1LXNlc3M=
*.172.65.* [0E6C] 11:11:01 <<< dXNlcm5hbWU9Im5vcmVwbHkiLHJlYWxtPSI3OTAwbm92YWRyaXZlLmNvbSIsbm9uY2U9Ik9HWXlPVEE1TXpnNU16bGgiLGNub25jZT0iZDZiOWY1ZWQiLG5jPSIwMDAwMDAwMSIsZGlnZXN0LXVyaT0ic210cC83OTAwbm92YWRyaXZlLmNvbSIscmVzcG9uc2U9MTNkOGJmNzQ1MDRiOGU0ODMzZGM1OGYzNzE4ZDg4M2M=
*.172.65.* [0E6C] 11:11:04 Authentication [SMTP] - Result=0, User=noreply, Method=4
*.172.65.* [0E6C] 11:11:04 >>> 535 5.7.8 Authentication credentials invalid
*.172.65.* [0E6C] 11:11:04 *** <> <> 0 0 00:00:00 INCOMPLETE-SESSION
*.172.65.* [0E6C] 11:11:04 Disconnected