Trying to authenticate via POP from Scanner

[derek.rose]

I'm trying to setup a KYOCERA FS1128MFP unit so I can scan to e-mail. It seems to be coming down to authentication issues, as shown here in the zimbra.log

Sep 24 11:07:27 zimbra-vm01 postfix/smtpd[14757]: NOQUEUE: reject: RCPT from <removed> 554 5.7.1 <user@domain.com>: Relay access denied; from=<user@domain.com> to=<user@domain.com> proto=ESMTP helo=<KM469920>

I'm guessing if I added the public IP to the MTA it would work, but I'm just testing this configuration so one of our customers can use it. Do I have to maintain the MTA for this or is there another way?

I have POP and POP over SSL enabled, over clear text is not currently enabled and I would prefer not to enable that.

Any tips are appreciated

[derek.rose]

It's worth mentioning I could try the clear text option but it's my understanding I have to restart the services to apply that, which I'd like to avoid during the day if it's just a test. Am thinking about doing it after hours, but would like to know if that is what is needed to avoid using the MTA field.