I'm at a loss to understand the doubts expressed about Yahoo Groups. The GQRP reflector which Graham G3MFJ & I run has over 2600 members and it works pretty smoothly for us.
If set correctly, you will never see a new member join and immediately start spamming. You can prevent attachments that might be harmful and there are a number of other controls to make life safer/easier. There has also hardly been any downtime since we started here in 1998.
You don't have to use the Yahoo web interface to post if you don't wish to - or even log into Yahoo to post. Just send to firstname.lastname@example.org
So given that this is now the new 4sqrp home, lets see how it goes and thanks to Don for all his hard work - I hope this works out a little easier.