group emails - settings question

[lesplan]

I'm wondering how to figure out what the best setting is for the Group emails setting?

I just sent out about 3,000 emails and some recipients are saying they did not get the email. They are in the MBM file / list but I downloaded the email history from auth.SMPT (the service that we use to send the emails) and the bottom 20% or so were not in the list (even though they appeared as 'sent' in MBM' ???? I have never experienced this before.

I had 10 selected in the Group emails setting? Is this too many and how do I find out what the best number is to use? What is the difference between 1 and all at once?

Thanks in advance for your time.

 

[stanbusk]

MaxBulk Mailer marks a message as sent as soon the server accepts it for delivery. It is explained here. The server accept a delivery with an explicit response. If a message is accepted and later discarded it is for a reason I ignore, only the server can respond to your question. Is it because of a spam filter? a server error?