Email Bounces – 2

@ sign bouncing on a trampolineThis is a continuation (and conclusion) of last week’s post.

More clues to look for in the text of the (rather cryptic) bounce message

Unable to relay or relaying prohibited

There could be several reasons for this message:

  • Your email connection might require authentication by logging onto your incoming server before attempting to send anything out (a setting in the email configuration if you use an email program such as Windows Live Mail)
  • The smtp mail server (ie the outgoing or sending server) that you are trying to use will not allow you to use it as your IP address does not identify you as a legitimate user of that server (for instance, if you are using a laptop with a wifi connection other than your own router at home)
  • The return address of the email message is at a domain other than that of the smtp server


There are dozens of lists on the internet containing the names of servers that are known or suspected to send spam. Your own ISP’s email servers could have got onto one or more such lists. Although completely innocent, your email may be failing to reach its destination because the recipient’s email server found your ISP’s email server on a blacklist they check against.

If this happens to you, you need to contact your ISP, explain that you think they’re on one or more blacklists and ask them to act to get themselves removed. A client of mine fell foul of this problem a few months ago. The reaction of the ISP was somewhat underwhelming in that they said they had tried to get removed but it was outside their control. Not very useful. In the end, we took advantage of a facility provided by Google whereby you can retain your own email address but have your messages routed through Google’s servers. Free of charge and it’s been working ever since (but a bit messy to set up).


This is not as serious as blacklisting. What it means is that the recipient’s email system will only receive email from specific (ie “whitelisted”) email addresses. You would need to contact the recipient by a means other than email in order to get your email address added to their whitelist.

Spam Filters

Look in the bounce message for words such as “blocked” or “suspected spam”

Your email may have been rejected by the recipient’s server as it looked like spam. There are certain things you must avoid when composing emails – eg don’t write in capital letters, don’t use multiple exclamation marks. I was just about to give specific examples of what not to do but then realised that the newsletter version of this blog post would probably get caught up in everyone’s spam filters. The reality, though, is that you are unlikely to know that your message has been rejcted for being suspected as spam. Spam messages aren’t normally bounced – just discarded or held in quarantine.

Non-Delivery Without Bounces

There are times when the recipient claims not to have received your email but you did not receive any bounce message. There are several possible causes of this:

  • Spam Filters – If your email has been blocked by a spam filter then you may not be informed by a bounce message. Your message will seem to have simply disappeared into the ether.
  • Junk Folder – The recipient’s email software (as opposed to the recipient’s email server) may have intercepted your message as spam and moved it directly to the recipient’s Junk folder. So if someone says they haven’t received your email the first thing to do is ask them to check their Junk folder.
  • Email Rules – The recipient may have set up their own rules in their email software to semi-automate the handling of incoming mail. One of these rules may have caught your message and dealt with it in an unexpected way. If you have reason to suspect this, you might ask the recipient to to perform a Windows search on some specific text in your email. If the message is in their system but has been moved somewhere unknown by a rule or filter then this may explain what’s happened.
  • Message or attachment too big – If you suspect this is the problem, try sending a short email with no attachment. If it gets through then it may have been that the incoming server rejected your message because either the message or an attachment was too big. Some email servers won’t accept attachments bigger than 5mb, others 10mb. If I’m sending someone a large attachment I always ask them to confirm receipt.

Conclusion: although bounces are a nuisance, the bounce messages often contain useful information – you just need to glean the information and ignore the machine-speak.