Mozilla Monitor website will be down for 2 hours starting 5/20/2025 at 6 AM PT. Visit our status site for updates.

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Can Thuderbird return E-mails if sent to an unknown address?

  • 5 replies
  • 1 has this problem
  • 38 views
  • Last reply by cerven

In some case I have sent an E-mail to another person but have missed a letter or number and it does not come back indicating an unknown address. Is this something that Thunderbird can add to the software? After Eudora departed a few years ago I switched to Thunderbird and like everything about it except this feature.

In some case I have sent an E-mail to another person but have missed a letter or number and it does not come back indicating an unknown address. Is this something that Thunderbird can add to the software? After Eudora departed a few years ago I switched to Thunderbird and like everything about it except this feature.

Chosen solution

If you send an e-mail to an e-mail address like 4e8d4f8e4f8e4f8e5wkj@gmail.com (you can be sure that e-mail address doesn't exist), then Gmail will send you a bounce-back message saying that the e-mail address doesn't exist, because they are the only ones that know for sure whether that address exists or not.

The same goes for @yahoo.com, @hotmail.com, and almost all major e-mail providers. They all will send you a bounce-back message if the e-mail address doesn't exist.

It is always the endpoint server that will say whether an e-mail address exists or not.

Eudora and Thunderbird are just e-mail programs. They have nothing to do with this process. They just send the e-mail. It was never Eudora that sent you such messages. It was the endpoint server.

Just to complicate things further...

The endpoint server for an e-mail address doesn't have to send such a bounce-back message to you. I administrate my own domain name and I can set it to do whatever I want for e-mails that are sent to non-existent addresses to my domain name. I can set the e-mail server to just delete them. I can set a "catch-all" address to send all such e-mails to. Or I can set the server to send bounce-back messages (which is what I have done).

Then there also the possibility that when you type the e-mail address in wrong, that "wrong" e-mail address might actually belong to someone. What they do with your e-mail is up to them. I suspect that most people will just ignore the e-mail.

Read this answer in context 👍 1

All Replies (5)

As an e-mail program, Thunderbird can tell you if an e-mail address is not formatted correctly (like missing the @ symbol), but it cannot tell you if a properly formatted e-mail address is the wrong address.

Thunderbird can indicate whether an e-mail address you have typed into the "To" field of a new e-mail is in your Address Book or not. If it is in your Address Book, it will be black. If it is not in your Address Book, what you have typed will be in red.

I have found the second part of your answer useful. However it looks like we will not get a rejected E-mail returned to us until someone comes up with a solution. If memory serves me correct I think Eudora used to send E-mails back if the mailing address not out there.

In case you're not sure about an e-mail address you can also ask Thunderbird to send a return receipt or delivery notification.

A return receipt is typically sent by the receiving user: he is prompted that you want to receive a notification and he can decide to send or not send it to you.

Delivery notifications are sent by the mail system to confirm that the message has been delivered to the users inbox. Unfortunately most mail systems don't send those notifications anymore, because they are also used by spammers to find real mail addresses.

You can find the option to send either of those notifications in the mail compose window under the Options menu…

Chosen Solution

If you send an e-mail to an e-mail address like 4e8d4f8e4f8e4f8e5wkj@gmail.com (you can be sure that e-mail address doesn't exist), then Gmail will send you a bounce-back message saying that the e-mail address doesn't exist, because they are the only ones that know for sure whether that address exists or not.

The same goes for @yahoo.com, @hotmail.com, and almost all major e-mail providers. They all will send you a bounce-back message if the e-mail address doesn't exist.

It is always the endpoint server that will say whether an e-mail address exists or not.

Eudora and Thunderbird are just e-mail programs. They have nothing to do with this process. They just send the e-mail. It was never Eudora that sent you such messages. It was the endpoint server.

Just to complicate things further...

The endpoint server for an e-mail address doesn't have to send such a bounce-back message to you. I administrate my own domain name and I can set it to do whatever I want for e-mails that are sent to non-existent addresses to my domain name. I can set the e-mail server to just delete them. I can set a "catch-all" address to send all such e-mails to. Or I can set the server to send bounce-back messages (which is what I have done).

Then there also the possibility that when you type the e-mail address in wrong, that "wrong" e-mail address might actually belong to someone. What they do with your e-mail is up to them. I suspect that most people will just ignore the e-mail.

Thanks for this prompt reply and your clear explanation of the process. I now realize that It is up to the sender to keep all addresses up to date.