Please explain further exactly what happens: 1. What type is the account (IMAP or POP)? 2. Who is your email service provider? 3. Which version of Thunderbird are you using? 4. Are you able to log in to the account via webmail (through a browser) and send/read emails? 5. Which server settings are currently in use by Thunderbird? 6. Which error messages do you receive, if any? What changed right before this problem started, for example, did you upgrade to Thunderbird v78 from an older version?

This is the best I can do, not being computer savvy. 1. I MAP, 2. RCN 3. 78.1.1(32 bit) 4. I can receive and send messages from my RCN account using my browser and my iPad. Messages sent out from Thunderbird do get sent, but I get an error message saying the message cannot be saved/ 5. Not too sure about this one. Server port 143 incoming SMPT server port 25 6. I receive no error message. It just keeps going round and round, but never opens. No problems before I updated to version 78.1.1. Avast had said that it needed updating.

5. Not too sure about this one. Server port 143 incoming SMPT server port 25

Please confirm these via Tools > Account Settings > Server Settings. It's important that you use the right server settings. Post a screenshot of those settings.

Before I respond with your question, there are 3 accounts with rcn.com and previously I had received a mail delivery failure 554 and it repeated itself about 50 times. I put it into trash and I can't delete it. The other 2 accounts had no such message.

Okay. I don't know how to post a screen shot, but here is the information: Server type IMAP server name rcn.com port 143 security settings STARTTLS server settings: check for new messages at start up and every 10 minutes. When I delete a message I move it to trash and clean it out periodically. Thanks for continuing to try to help me. Joan

disable email scanning in avast and see if that helps. Avast has a longish history of truly messing up email, especially over SSL/TLS connections.

Stan already asked in his own way, but for us to better investigate this issue, we'll need some more information.

Could you please do the following?

1. Open the menu > Help > Troubleshooting Information, then click Copy text to Clipboard.
2. Go to https://pastebin.com, paste the info from your Troubleshooting Information page, use the Create New Paste button to create a page containing your info, then copy the resulting URL (address) of the page created.
3. Open a reply to this post, and paste the link to your troubleshooting information you just copied.