I have been trying to sort out all my email lists etc as I have been organising the new Sempertex newsletter which has over 600 new emails to add to the lists I already have.
I decided to code every list so that those who received more than one email from me I could easily see what other list they/you were on and delete so that I was not sending out too many duplicate emails and annoying people. So tonight is the night my computer decides to play up and for some reason only known to itself it decides to put all me emails in the outbox and not send them      
It's taken 90 mins to send 6 emails, have decided to just shut it down now and go to bed and try again in the morning, the fun we have.

I know what that can be like, Graham.

Depending on how you are organising them, and how many are on more than single list, it can be useful to have amalgamated lists with embedded lists within lists.

If you aren't already doing this, its often useful to embedd lists within other lists, so the UK twisters list has in IT's list UK conventions, UK social email etc.  It can become quite streamlined with a little flowchart and small amount of organising, and not for every person, but I believe you have the skills to run it better.

Do you have that type of setup yet?

I always have 99 emails per list otherwise it will bounce back, and quite a few lists now, growing all the time.
Not sure about what this embedding is but perhaps will need to spend some time investigating.

Just sending the last one out now, still having slight problems but at least they eventually went