Zimbra unable to email from mobile after upgrade to 8.0.3

Question

We recently upgraded our Zimbra FOSS email server to version 8.0.3, and since that upgrade all cell phones (Android and iPhone) give the error 'The recipient "email@domain.com" was rejected by the server because it does not allow relaying.'

I can not find anything that looks to have changed. Does anyone know if this is a known issue with version 8.0.3?

Thanks for any help with this issue... I'm not having any luck fixing it, or even finding anything that actually pertains to it...

Edit

As an update:  I found the following information in my Zimbra.log...

Mar 26 16:58:21 server postfix/smtpd[22783]: NOQUEUE: reject: RCPT from 29.sub-174-237-227.myvzw.com[174.237.227.29]: 554 5.7.1 Service unavailable; Client host [174.237.227.29] blocked using zen.spamhaus.org; http://www.spamhaus.org/query/bl?ip=174.237.227.29; from=<me@server.net> to=<me@server.net> proto=ESMTP helo=<[10.246.232.147]>

Answer 1

After researching the above edit, we found that the problem was (apparently) related to SpamHaus.org blocking the relaying of emails through the cell providers into Zimbra. I turned off SpamHaus, and everything is working fine now...

Hope that helps if anyone else has this issue...