What are your settings, compared to these ones? The error indicates the User Name is the part before the @, rather than the full address.

If you have the correct settings, the problem may be due to the TLS version.

Sorry. It did not work. Tried those settings. It did not accept the password.

Looked up TLS settings. It says my TLS minimum is 3 and max is 4.

For many years it worked with user name perless, port 587, and 'password submitted insecurely'. In fact, it worked on 4/20 and 4/21. It stopped working on this machine on 4/22, the day it upgraded to 78.10 at 5:28 pm, but it still works with those settings on an old mac and two iphones.

My incoming mail is not optonline. It's a pop mailbox on rcn. And it's working fine.

?

Have you checked for an antivirus or firewall that is blocking the new TB? Was it working on a previous branch of 78, or was the last update from 68 to 78?

It was working fine on 78.9 on 4/20 and 4/21. We have removed Norton two months ago. It does not show up when I go to Find. Is there any other place that I should look for it?

I would check the OS X login apps for Norton or any other app that potentially interferes with TB, including online backups or password managers. Try also deleting the passwords from Saved Passwords in Preferences/Privacy & Security, restarting TB, and entering the password when prompted.

I didn't find passwords saved anywhere but Firefox and TB. In Preferences/Privacy and Security will it remove the login as well as the password? It looks like that's what it's saying. It says that the password was changed today when I entered it today trying to unlock the server. It says that the user name and date for the pop mailbox (which works) is perless and 2016.

The login is the User Name, which is set in Server Settings in Account Settings. If you delete the passwords, you will be asked to enter them after a TB restart. The password for the outgoing should be the same as for the incoming, if you have the account properly set up.

I tried deleting it in server settings, and I tried it as SSL/TLS, and neither worked. The password is not the same as incoming. Incoming has two characters more. I looked it up. Don't know why we set it up that way a long time ago, but we did. I also looked at password on iPhone and it is the one I've been using.

Tearing my hair out.

I've never seen an example of an account using different passwords for incoming and outgoing on the same server. I suggest you try adding the account using the settings in my first reply, but in a separate profile. Help/Troubleshooting, about:profiles, to create and manage profiles.

I never said it was the same server. The incoming server is pop.rcn.com

For years, the outgoing server was my internet provider, optimum, mail.optonline.net. that is no longer my internet provider. My internet provider, Verizon Fios does not provide email services.

I have tried to enter rcn's outgoing mailbox, but it also does not seem to be working. I am not sure that I have the correct parameters for it. I can't get a tech on the phone that knows. They host my website and the incoming pop mailbox is working.

When you said in your first post, "The error indicates the User Name is the part before the @, rather than the full address." What do you mean. Should the User Name be the full address? Or should it be the part before the @? It was the part before the @ for years and it worked.

If you have a POP account with RCN, you should be able to send over their server, smtp.rcn.com on 587, STARTTLS security, authentication = normal password, User Name = email address. If Optonline is not your ISP, why are you trying to send on their server?

https://help.rcn.com/portal/articles/2136

Most providers require the full email address for the User Name, some just the part before @.

You're not going to believe what I just found out. I've been calling rcn since it happened, and kept getting a woman who said, we're working from home, and I'll get the email person to get back to you in 48 hours. He never got back to me. I called this morning, and she said he would call by 4, EDT. He didn't.

So I called at 4:15 and got a guy named Michael who looked it up and said that the account was locked because it had spam, and they were afraid someone was trying to hack it. I told him that it was an art studio, and that they should unlock it.

I've now got the outgoing smtp server working, with input just as you indicated.

THANK YOU A MILLION!!

Same thing is happening to me over last few days with Verizon/net Before the T bird update.

  Not taking PW but is ok if I log in through browser.