You will only get a bounce back email from server under specific conditions.

1. Mailbox does not exist - maybe email address not correctly typed or email address no longer exists as user stopped account.

2. Mailbox is full - the owner of email address has used up all their server quota so server cannot receive any emails until some get deleted to create space.

3. Cannot be sent - maybe you have exceeded a sending limit or server needs authentication from sender or server is temporarilly down etc.

4. Refused by server due to Server Spam filters rejecting either content of email or IP address or email address.

But if you just sent an email intended for person A, but you accidentally sent it to person B then there's nothing wrong with email and it got delivered. Person B may have ignored it or realised it's not for them and deleted it. Or they may not have even looked at their emails, so do not know they have received it. But there is no reason for a server to bounce it back. The email address was ok and the server mailbox received it.

There is no way Thunderbird nor any server can know who you want to send to, only you know what email address should be entered. So basically, you just sent a perfectly good email but not necessarilly to the correct person.

My mailbox was full, exceeded quota, so I deleted most of backlog. I still cannot receive or send without receiving the Bounced Message Notification. Any idea what to do to get system working properly?

re :My mailbox was full, exceeded quota, so I deleted most of backlog.

Did you delete via Thunderbird or via webmail account ?

If via webmail account: After deleting : Did you then empty the server Trash and Spam folders? Are you using Google because Google quota includes Emails and anything else stored on their servers which includes Photos.

If you access the webmail account via a browser are you now receiving new mail into the Webmail account ?

In Thunderbird Clean up folders - some accounts need to compact fodlers to completely remove all traces of emails to force them to be deleted off server.

• Right click on folders and select 'compact'
• Empty Junk/Spam and then compact

If you use an Imap mail account:

• Right click on Inbox and select Properties
• Select the 'Quota' tab

What does it say?

What type of account are you using Pop or Imap? What server are you talking about ? I mean the one which has your emails eg: gmail, comcast, BT etc

Re: Bounced Message Notification. Please post an image of that Bounced Message as the wording helps to identify the issue.