Some tips for troubleshooting email that bounces

The key to solving any email problem is to carefully interpret the symptoms of non-delivery.

Many users interpret email issues as falling into a specific category – in fact – email problem may be very unique.

If you are getting an error message always provide this exact message to the call centre.

Email bounce messages often start with 5.X.X for example, 5.5.0 Relay Access Denied.

Make a note of this message when contacting us for support.

Relay Access Denied

Email bounces are easy to interpret because all the information are included in the message. The most common error is as follow:

May 12 16:24:00 mx postfix/smtpd[4563]: connect from unknown[]
May 12 16:24:00 mx postfix/smtpd[4563]: setting up TLS connection from unknown[]
May 12 16:24:00 mx postfix/smtpd[4563]: Anonymous TLS connection established from unknown[]: TLSv1 with cipher AES128-SHA (128/128 bits)
May 12 16:24:01 mx postfix/smtpd[4563]: NOQUEUE: reject: RCPT from unknown[]: 554 5.7.1 <>: Relay access denied; from=<> to=<> proto=ESMTP helo=

Relay Access Denied is easy to resolve. This means Outgoing Server Authentication is not set. Always be sure to tick “Outgoing Server Requires Authentication’ with a Snowball Hosted email address. By default Outlook or any other email client will tick ‘Logon on using same settings as Incoming Mail Server’ – which is correct.

User unknown in virtual mailbox table

An error occurred while sending mail. The mail server responded: 5.1.1 <>: Recipient address rejected: User unknown in virtual mailbox table. Please check the message recipient and try again.

This error is also very easy to resolve. It means there is no such email address attached to a domain. So look for typo’s or see if the email address truly exists. Sometimes this error appears when a domain is disabled.

RBL’s like Spamhaus

The following recipient(s) cannot be reached:

‘Homer Simpson’ on 2013/11/18 06:25 AM

554 5.7.1 Service unavailable; Client host [] blocked using;

It is best reported to or to let the engineers investigate the issue.


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