Messages "sent" but not received
I have sent messages using the same recipients (~30) many times but over the weekend they are not being received. The messages show up in the sent folder and I do not get the "too many recipients" warning. However, no one is receiving the messages. I believe the problem has to do with the number of recipients because if I send to just a few the message is received.
Opaite Mbohovái (3)
If they're in the sent folder, they were sent. However, you might check with your email host. They may have a policy on number of messages sent per day. Sending multiple messages to 30 recipients may be over the top.
The same email host I've used for years.
Thunderbird is just a messenger; it does not administer quotas. You stated that the messages show as sent. But you don't want to pursue the email host that is receiving and sending to recipients. I have no further suggestions.