Only 1 account. Will try your fix, but where do I find the "menu app icon"?

App Menu is the three bars, typically top right

The password was fine, but it occurred to me that if that were not the case I wouldn't be able to send 'To' emails either. It is only 'Bcc' that is a problem. If I go into Cox web mail directly I can Bcc as always. Somehow the Bcc in Thunderbird is not getting through to Cox, it is being stopped by some remote, hidden setting of some kind. Do you suppose there is a way to completely reset Thunderbird back to its factory set condition without the loss of all of my accumulated files/folders?

I was about to write that there is nothing in Thunderbird that would block Bcc, but then I remembered in version 91 we changed smtp (which is wnat sends mail), which hadn't changed in the previous decade so it had been bug free prior to version 91. For example we had two fixed bugs

• Cannot send email messages with Bcc recipients
• Send bcc only messages from Outbox doesn't work

So the possibility does exist for there to be a Thunderbird bug. Something to take into cosideration. However, given that it does work for you previously?, points in the direction that the cause might not be Thunderbird.

p.s. I know of no settings, no possibility for reset, no reinstall process that would possibly help.

p.p.s. bugs reports new in teh past year https://mzl.la/3x0el6J

I haven't been able to Bcc for about a month I'm guessing. Although time consuming, I think what I will do is back up my files/folders and completely purge Thunderbird from my PC, then re-install. I'm sure that process will come with unforseen problems but I'm getting desperate. I've used TB and the TB calendar for so many years (w/o a problem) that the thought of scrapping it altogether is more than I want to deal with right now. I may not get to this today or tomorrow due to an emergency medical problem with my wife, but I won't delay much longer.

Thanks for your assistance.

Because I put my wife's PC on TB a couple weeks ago and she doesn't have the problem I hope that a fresh install, after a 'Revo' uninstall, should (?) eliminate any existing problem. I can think of no other solution.

Thanks again.

This issue is way out of my wheelhouse, but I am absolutely certain it is not my provider that is preventing me from using bcc feature. I am getting the same msg that everyone is getting, referencing Outgoing settings etc. Adding my own address in the TO box simply produces the same message PLUS "Recipient already specified" So, I tried using BCC from my provider AOL and the BCC option worked fine. This is definitely a Mozilla issue.

I agree. What I don't understand is why I have the problem yet my wife, with a fresh install of Thunderbird with all other connections the same, does NOT have the problem. I fear that a total purge of Thunderbird, with a fresh re-install is not going to solve the issue, but it's about the only thing remaining to try.

Thank you for your response.

I did a full and complete uninstall using Revo Uninstaller, which deletes all vestiges of the program. Totally clean. Then I did a fresh install, resetting everything from scratch. Everything went very smooth - still can't send Bcc!!

It seems like this problem started within this month (April 2022). If I want to share something with 3 people, I thought that was the problem. I whittled it down to I can't send a BCC email to one person and no attachment. The fact that it works perfectly using TO: tells me it isn't the Internet provider. It's Thunderbird!

Yes, you are right, put just one address in Bcc and it won't go. However, if you include an address in the SAME EMAIL that is NOT in Bcc, it sends w/o a problem. Over the weekend I totally uninstalled Thunderbird (again), including any file associated with TB, did another totally clean re-install, but no help, it simply won't send Bcc. I wonder if anyone at Thunderbird is reading these?

If you put an address in a TO field and an address in a Bcc field and send... Does the person in the TO field receive email ? If yes, then email was sent to server and server accepted it and then deals with the actual sending. Thunderbird only sends to server, it is not involved beyond that.

re :So, I tried using BCC from my provider AOL and the BCC option worked fine.

It might seem ok but it is irrelevant as the process is not the same. The smtp server has not received an incoming request to send.

1. Many servers will not send Bcc if there is no email address in a TO field. 2. Server may not send Bcc if one of those email addresses is blacklisted. 3. Server may not send Bcc if you are not using a secure Connection eg: SSL/TLS over port 465 4. Some servers have changed sending requirements and may require you to set an app specific password. This effects yahoo servers and those who use a yahoo server : https://help.aol.com/articles/Create-and-manage-app-password?

https://www.cox.com/residential/support/changing-email-server-settings-for-mozilla-thunderbird.html

If you put email address in TO and Bcc and it did not send at all then check to see if you have correct smtp settings - that the email account is actually using the correct smtp server for that account.

I've seen people have two email addresses using same server, but they have managed to set up both accounts to send using identical smtp, so one account is not using it's own smtp. Then it causes a problem. So always double check the account really is using it's own smtp.

Also check to see if you now need to set up 'app specific passwords' as this could be a password issue.

While I am glad and certainly appreciate that people are still occasionally sending responses to this post/problem nothing has turned into a 'solution'. If I put an address in the TO field and an address in the Bcc field, the TO field will send w/o a problem. The Bcc send, in that particular configuration, is simply ignored, not even an error notification. If I send a Bcc only, regardles of the address or how many addresses, I will get an error notification. I am using Cox and they require no additional passwords. There has been no changes made to their server, one day I was sending Bcc (10 years+) and the next - nothing. If I want to broadcast an email using Bcc, I now must send the email to my Gmail account, then re-send it using Bcc.

Again, I do thank you for trying.

Please do this to see what info appears.

Menu app icon > Tools > Developer Tools > Select 'Error console' It opens in a new window.

Click on the top left bin icon to clear contents. Create email using bcc and send.

Then look in the error console and post an image showing its contents.

This is what came up:

mailnews.smtp: Command failed: 552 <tiger-rka07@cox.net> message rejected. Refer to Error Codes section at https://www.cox.com/residential/support/email-error-codes.html for more information. AUP#CXSNDR; currentAction=_actionStream SmtpClient.jsm:504:19

   _onCommand resource:///modules/SmtpClient.jsm:504
   _parse resource:///modules/SmtpClient.jsm:360
   _onData resource:///modules/SmtpClient.jsm:414

mailnews.smtp: Message sending failed. SmtpClient.jsm:1291:21 mailnews.send: Sending failed; An error occurred while sending mail. The mail server responded: <tiger-rka07@cox.net> message rejected. Refer to Error Codes section at https://www.cox.com/residential/support/email-error-codes.html for more information. AUP#CXSNDR. Please check the message and try again., exitCode=2153066725, originalMsgURI= MessageSend.jsm:336:27

​

The server received and rejected email. Two error codes mentioned. 552: 552 - [$(_id) attachment extension is forbidden] The message has been rejected because it contains an attachment with one of the following prohibited file types, which commonly contain viruses: .shb, .shs, .vbe, .vbs, .wsc, .wsf, .wsh, .pif, .msc, .msi, .msp, .reg, .sct, .bat, .chm, .isp, .cpl, .js, .jse, .scr, .exe. Ensure that your mailings do not contain attachments with these file types.

CXSNDR: There was a problem with the sender's domain. Your email failed authentication checks against your sending domain's SPF, DomainKeys, or DKIM policy.

This sounds like an Anti-Spam server filter objecting to something.

You have already stated there is no 'signature' html file etc. Confirm: Does content contain any inline images or links or attachments? Is content just text?

Do you know if your Anti-Virus product is adding anything to your emails? Check it out. For example: AVG and Avast Antivirus may include a Virus-free message (previously an email signature) at the bottom of your outgoing emails to let your recipients know that the email has been scanned for malware. This setting is enabled by default.

If this is occuring then disable it. What Anti-Virus product do you use?

please confirm the following: Menu app icon > Preferences > General scroll to bottom and click on 'Config Editor' It opens in new tab In search type : undisclosed Look for : mail.compose.add_undisclosed_recipients Confirm this is set to 'True'

. I tried using BCC from my provider AOL and the BCC option worked fine. This is definitely a Mozilla issue.

Clarity: If you read previous comment by Matt, you would have read this "using web mail and using their SMTP service is not the same thing. Don't let them get away with trying to say it is. They don't even use the same SMTP Server to send mail." In a nutshell....Sending using webmail account is not the same. You are already logged onto the server. When using an email client you are sending to the server using smtp protocol. So basically, the fact you can use webmail is irrelevant.

AOL is using the yahoo servers, so they have a tendency to be a pain. Yahoo do tend to need the TO field with valid email address - this has been reported many times on yahoo forums. They have also been upping security, so..... have you created and use an app specific password instead of password or are you using imap and Authentication Method : OAuth2 for incoming and outgoing smtp?

Follow same instructions to check error console - what do you get. Post an image.

Just because it may seem like you are having the same problem - it does not mean the cause is the same.