How can I get Thunderbird to allow me to send or respond to a group message of more than five recipients?

   Open Thunderbird Settings and scroll down to Config Editor.(at very bottom of Settings window)
   Search for mailnews.tcptimeout. - there are many pages of processes but they're alphabetical. This one is about 60% of the way down the page. 
   Change the default value from 100 to a higher number (maybe try 500) - simply click on the pencil (edit) and change the 100 to 500 and then click the check mark. The change will be made instantly.
   Then return to main page and see if it works."

A friend sent me the following to try. Resetting the timeout fixed the problem (did a test email to 32 recipients)... "The problem has to be either with Thunderbird settings or with the Spectrum server. In talking to Spectrum, it's not them. Here's what I learned - A single email can have up to 99 recipients total. This includes the To:, CC:, and BCC: fields combined. The number of recipients per message cannot exceed 100 (limits can change due to email abuse patterns). The number of recipients per hour is limited to 1,000. So, the issue is with your Thunderbird client. My guess is that it times out before it can send out more than 5 which may be due to the speed of your internet service or your wireless card in the computer. The first thing I'd suggest is you do is increase the timeout to 500 - the default is 100 which is pretty short. Here's how to do that: Adjust Timeout in Thunderbird: Open Thunderbird Settings and scroll down to Config Editor.(at very bottom of Settings window) Search for mailnews.tcptimeout. - there are many pages of processes but they're alphabetical. This one is about 60% of the way down the page. Change the default value from 100 to a higher number (maybe try 500) - simply click on the pencil (edit) and change the 100 to 500 and then click the check mark. The change will be made instantly. Then return to main page and see if it works."