Newsletter quits mailing out half way through

A mass email was supposed to be sent on 7/17/2012 to about 4000 of my friend's customers but only about 1800 were sent.

She is using smtpauth from an authenticated email on her domain.

Email logs show 1809 emails sent (some are errors, some reattempts, most are successes) over three minutes from 7/17/2012 16:01 to 7/17/2012 16:03, at which point it apparently fails. Check mail log, most go out, some errors.

I have settings in WHM that allow unlimited emails to be sent. Nothing unusual was happening on my server that day.

Took me a while to figure out what list was being used for the mailing and if it was skipping some addresses or what. I finally realized the list is the same one appearing on the admin newsletter page that allows you to mail a message to everyone, a smaller group or to individual customers. It includes the names of every client in alphabetic order and this appears to be the list used by the mailer.

I found a failure point after which emails seemed not to be sent. Nothing unusual about the email.

Any ideas here?

The sheer large number of addresses to send to takes a long time. It could be that the server timed out while trying to do the sending.
Or it could be that the smtp server rejected a particular address and caused the script to abort.

If these problems can't be overcome with your server, then it's certainly a good idea to send out your emails via a mailing service such as MailChimp or Constant Contact (who offers a free trial) and use the Email Address Exporter plugin to extract the email addresses from your store for periodic updates to the mailing service database.

Thanks for your reply.

DrByte:

The sheer large number of addresses to send to takes a long time. It could be that the server timed out while trying to do the sending.
Or it could be that the smtp server rejected a particular address and caused the script to abort.

There was no error associated with the apparent last email sent in the log and my vps seemed to operating fine (no load spikes, etc.). I'll see what my host has to say about the server timing out as a possibility.