Try it with the correct settings: mail.twc.com, 587, STARTTLS, normal password, email address.

https://www.spectrum.net/support/internet/email-settings/

Thanks, but I just continue to see "sender rejected" error messages, as if all of a sudden my email name and address has been rendered invalid. I'm starting to think somebody at Spectrum changed something and didn't tell anyone. And the Spectrum site and support people are useless/worthless.

And BTW, I AM able to send emails from the Spectrum webmail site -- using the same email name/address.

Do you have more than one Spectrum account?

Yes. I have one logon to pay my Spectrum bills and another to use their webmail.

So, is that two accounts in thunderbird? I ask because the error message is often tied to use of the wrong SMTP server. Please clarify.

Thanks for trying to help. I appreciate it.

I have multiple email addresses -- all with the same domain name. All are using the same SMTP server.

See https://support.mozilla.org/en-US/questions/1350593

You can have multiple Spectrum accounts on the same server, but there must be separate smtp that differ only in the User Name (email address.).

I have one Spectrum account that I use to pay my bills. I have a second that I use to access their webmail service.

I have four Thunderbird email addresses all with the same domain name.

I have one SMTP server.

The domain name is entirely irrelevant in this situation. Spectrum insists the email address in the username field of the Outgoing server(SMTP) used to send the mail matches the email address in the from line of the email.

That's one of the things that's so confusing. The names match perfectly.

The other thing is: I was able to send one minute and then not the next. It's like Spectrum changed/updated something and didn't tell anyone.

The third bit of confusion is: I'm able to send from that same exact username/email using my webmail account.

Nothing makes any sense.

- click to account settings - scroll down to Outgoing servers (SMTP) and open that menu - there MUST be one smtp entry for each account and each should have a unique email id in the USER NAME field - edit the DESCRIPTION field for each to have the email id that is in the USER NAME field - this is for documentation only - now, back to account settings pane, highlight each account name and check the bottom line for that account, the line that points to the SMTP server. if it is showing the wrong email id, click the dropdown arrow and select the proper one. - doing the above steps will ensure that all accounts' SMTP servers are connected.

The web mail is a web site and mail does not come into it. As they all want folk on their advertising driven website, they devote resources to making the web pages work. With something like 95% of their customers using the web mail offering guess what part of their bu8siness gets a very low priority.

You are able to send one minute, but not the next. Does it come back in say 24hours? Perhaps you need to have a look at this stuff as Spectrum do no inspire any confidence in me at all. https://www.spectrum.net/support/internet/charter-postmaster-services

David -- My Thunderbird accounts only have one SMTP server. All my accounts used to be able to send though that one server successfully.

However you do it, the sending email address must match the SMTP email address. If that is not true, you will continue receiving that error message. Email providers sometimes tighten their security without telling anyone, even their own tech support staff.

Matt -- I was able to send successfully the morning of 1/28/25. I was unable to send emails in that afternoon. Obviously, I changed no settings.

I have not been able to send since, despite spending hours changing every setting I could find.

I even tried looking into the header of the last email I sent successfully it see if there was some reference to the SMTP server settings in there.

And I share your contempt for Spectrum. The only thing worse than their service is their support team.

David -- addresses match.

Puzzling. You have multiple accounts with one SMTP server - and all the account email accounts match the one in the SMTP server? Something is missing in this thread. Normally, each account has a unique email address and, if so, must have its own SMTP server. Please clarify. How can the addresses match? Thanks.

David -- I think I understand the confusion. You are of the opinion that each email account should have its own SMTP server so that the usernames match in the config, yes?

All I can say at this point is that all my email accounts used to use the same SMTP server (and config) for years without incident.

My only thought at this point is that the different accounts are subaccounts of the same primary account, but Spectrum changed the ability to do that on 1/28/25, and now require separate SMTP server configs (same server -- different configs).

However, that still doesn't explain why I was able to send an email that morning, and NOT be able to send an email from the same account later that afternoon.

Thank you Spectrum, once again, for introducing chaos into my life. I never had to log into the SMTP server before, but now I do.

Obviously, I have to log into the POP server to receive and now; I have to log into the SMTP server to send.

After creating a SMTP server config for each email account, I am now able to send from each.

I'm grateful to those who helped and tried to help.