I sent out an email to about 10 people. Looking at it now in the sent folder, I see that the CC list has 33 email addresses, with some of the original 10 addresses duplicated many, many times!
Similar emails that I have afterwards, sent with all of the recipients as BCCs instead, don't appear to have this duplication.
What could have happened? I emailed a few people in the list, singularly, to see if they got duplicate emails. They are reporting that they did NOT get duplicate emails.
I'm using a new Bluehost email address that has been working fine up until now. I don't know if the problem is on the Thunderbird side or the Bluehost side.
Windows 7 Pro, current version of Thunderbird.