Imagine those bundles being created and queued almost at the same time. Mail servers are extremely efficient at 1 job and that is to deliver mail. This process is completely impartial and normally goes on a first in, first out base. It doesn't know about big or small, it only knows about mails in/mails out.

As an example from one of the mail servers, I administer: right now there are 16 mail queues open which means that mail is waiting to be delivered to 16 different destinations to an unknown number of receipients. This particular mail server seems to be blacklisted (=they refuse to receive mail from it) by mac.com so there are 180+ msgs in the queue and they will sit there until mac.com decides to like this server again or the 3 days waiting period are up whichever comes first. Until that time, all msgs for mac.com sit there...let's say hastypastry.net was in a similar situation then all member having a mail address at mac.com would have to wait.

A small provider is more likely to have some spam prevention measurements in place than a big one. It may accept less receipients per mail than a big one or it might use what is called greylisting (the 1st mail from an unknown provider will be refused on principle; spammers hopefully won't try again whereas legal mail server will try again after a certain time) or it may have other anti spam tactics in place...all of them will at least delay the mail delivery (greylisting) if not make it impossible (no of receipients over the limit). In the latter case, it may even lock out the offending sending server for a time completely so you wouldn't ever get the mail.

In the case of delaying tactics, the mailqueue goes to the back of the queue to be sent and waits its next turn which will normally be around 20 mins later. The more times it is refused the longer it will wait before trying again.

I use the word "normally" a lot here. This is because everything I said, all times, etc. can be adjusted by the mail admins.

These are just some of the things that can go wrong; looking at all the different ways mail can and does go wrong it is sometimes very surprising that any mail arrives where it is supposed to go.

As JL gets a msg whenever a mail couldn't be delivered, he could, in theory, resend those mails but I would bet he doesn't. It is just plain too much work. A real life example from an announcement mailing list that runs here with around 2500 receipients. For every mail that is sent, we get back several 100KBs of plain text bounce msgs immediately after sending and that again over the next few days as mail servers return errors in their own sweet time. Some of them accept the mail but return errors up to 2 weeks later. Now, bounces are plain text and contain no pictures and/or formatting...I'd say on that list about 1/5th of the member addresses produce bounces. So is it reasonable to expect the list owner to clean up 500 addresses manually for every mail he sends?

Let's apply that to BT. JL sent about 50'000 msgs (if he did send a mass mailing), 1/5th bounces back (=10'000)...would anybody expect him to clean up 10'000 mail addresses manually? No? Good, because he won't.

Have I bored everybody to tears yet?

cheers
eve