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Outgoing email is slow or doesn’t arrive in your recipient’s mailbox

This article was posted in: Email

Messages you send to other can be delayed, or sometimes they are actually delivered, but due to spam filtering at the other end, the message ends up in a Junk Email folder or never actually reaches your recipient's mailbox.

There can be many reasons for this to happen, but two common explanations are given here


Some ISPs emply a technique known as Greylisting.

Greylisting works on the basis of triads. A triad is a composite of:

  • Sender Email Address
  • Sender Mail Server IP Address
  • Recipient Email Address

Upon receipt of an incoming message, the email system checks an internal database of previously encountered triads. If a new triad is encountered then the server says "Sorry, I can't deal with your message right now, please try again in a short while". In SMTP language, this is known as deferring a message, and the sending server is given an error code 451 (temporarily unable to accept).

The sending mail server, if correctly configured, will queue the message, and try to send it again after a short while (usually a few minutes).

The reason for Greylisting is because most spammers use badly configured or hijacked mail servers, which won't handle the deferrement, and usually give up (they are usually trying to send so many messages that the work involved in retrying is just not economical for them - or possible).

So, after a few minutes, the sending server tries again - Our servers usually retry after 15 minutes initially. This time the triad is recognised and the message is accepted.

Checking if a message was sent successfully

We are only responsible for the message up to the point at which it is accepted by the foreign mail system. Once we receive acknowledgement from the foreign system that it has been received successfully, our servers log the transmission as a success.

You can check this yourself by clicking on the Track Delivery icon in cPanel (look in the Email section of icons)

To check what happened to a particular message enter the recipient's email address in the box as shown, and click the Show All or Show Blocked & Failed buttons, or use the various tick boxes to refine your search. If you cannot find a satisfactory answer here, please raise a support request providing us with the following information:

  • Sender and recipient addresses of the failed message
  • The exact date/time it was sent
  • Any error received at send-time or afterwards