I have an Ubuntu raring server running postfix/dovecot as an email server, with tumgreyspf doing greylisting and SPF checks. My problem is that I also have a backup MX server, that is supposed to store my emails temporarily, should my main server ever fails. It usually rejects receiving emails if it finds the main server online and functional. The problem is when it does need to do its job, tumgreyspf rejects all emails from the backup MX with an error like this: Jun 27 16:18:13 hamra postfix/smtpd[28732]: NOQUEUE: reject: RCPT from mxbackup.mydomain.com[x.x.x.x]: 550 5.7.1 <[email protected]>: Recipient address rejected: QUEUE_ID="" SPF Reports: 'SPF fail - not authorized'; from=<[email protected]> to=<[email protected]> proto=SMTP helo=<mxbackup.mydomain.com> any ideas?