Issue with HTML email returns

[derekjackson]

Hi,
I've just had my first (mainly) unsuccessful attempt at an email mailout.

We sent out our company Christmas message to around 1500 people. We copied them in chunks of around 300 into the Outlook 'BCC' field. The content was a single image with a hyperlink to our website when clicked.

Unfortunately we've had about 1400 returned. Although we'll be using something like PHPlist for the next attempt, I've been asked to find out why they were returned. For some it was simple issues like the email address not being valid, but the majority had the error '#554 Transaction Failed'.

Any ideas what would cause this? Could it be some email programs picking up the fact we sent it in bulk, classing it as spam, and rejecting it? Any advice appreciated!

I should probably add that we happily send individual emails to these addresses normally with no problems, so we're not blacklisted by them...

Thanks,
Derek