Random recieves when sending to large list

[skullmonkey]

Hi,
something weird is happening.
For some time if I send to 20 people, they get the mail good. If I add them to a list of 500 they randomly get the mail. Only 3-4 get the mail, and the rest don't. What might be the problem?

I have dedicated SMTP server that is used for bulk mailings.

Thanks,
skullmonkey

 

[stanbusk]

What does the MaxBulk Mailer delivery report say? All sent?

 

[skullmonkey]

Yes. All done, all successful.

 

[stanbusk]

Can you paste the delivery report here?