What are your settings? These are for Spectrum:

mobile.charter.net. for both the incoming (IMAP port 993) and outgoing (port 587) servers, with Connection security = SSL/TLS, authentication = normal password, and User Name = email address.

https://www.spectrum.net/support/internet/outlook-2010-setup-chtr

Those are the settings I have for the servers. Is there anything else I should check ? This is the message I keep getting Login to server mobile.charter.net with username slyone13@rochester.rr.com failed.

Open Tools/Options/Security/Passwords/Saved Passwords and remove any obsolete passwords, if any, for incoming and outgoing servers. Also, what is your antivirus app, and is it scanning mail folders or secure connections?

I did not find any old passwords. I'm using Norton 360 for antivirus and overall security. I get a message saying twc does not accept authentification method. Please change. I have tried normal password and AuthO2

OAuth2 authentication is not supported by TWC, but they seem to offer both secure and insecure settings. You can try the insecure ones: mail.twc.com on port 143 (IMAP), connection security = none, authentication = password, transmitted insecurely, User Name = email address; port 587 for the outgoing SMTP server mail.twc.com, connection security = none, authentication = password, transmitted insecurely, User Name = email address.

https://www.roadrunneremail-rr.com/time-warner-cable-twc-imap-pop3-smtp-email-settings

I would definitely disable Email Scan in N360, but leave the real-time background scan in place.

https://support.norton.com/sp/en/us/home/current/solutions/v19117843

I did try the above suggestions with no success. I was on the phone with Spectrum for a couple hours no help there. Any other suggestions ? Thanks !

It is very common for Norton products to block new version of Thunderbird from access to the internet in their firewall component. I suggest you check that.

Thunderbird is not blocked from the internet. I can send and receive with Thunderbird from my secondary e-mail address which runs through a different server. I just can't connect with Spectrum. After 3 hours on the phone with Spectrum, they assure me all is good on their end.

I suggest you try the following. If Everything is cor (they say so), and our settiings are correct (they checked and verified them) then your connection is working. Clearly it is not. So lets see if their is a third party tool involved.

• Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, OSX

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.

Spectrum personnel are clueless as to why the server settings don't work other than mentioning 'latency' issues that they have not been able to resolve.

I saw a post a few weeks regarding IMAP settings for Thunderbird on Spectrum for road runner email addresses. Those settings didn't work. So after much fiddling on my own, here's what works for road runner email addresses (username@rochester.rr.com) here:

IMAP:

mail.twc.com port: 993 security: SSL/TLS

OUTGOING:

mobile.charter.net port: 587 security: SSL/TLS

This works EXCEPT for this error message on the bottom right hand corner.

Again Spectrum had no idea.

Those are the settings I have now. When trying to download messages it fails and I get the message timed out. When trying to send it asks for my password which I enter and it doesn't recognize it. The only "help" I get from the screen readers at Spectrum is we don't support 3rd party e-mail so it's not our problem. On the bright side we have a new ISP coming through our area by June. Less expensive and faster, bye-bye Spectrum. I appreciate your help.

that error is because Spectrum have had theur email server so badly configured it advertises siupport for features it does not implement. The error is harmless.

See my comment from a few minutes ago here to fix the error message https://support.mozilla.org/en-US/questions/1280365#answer-1292139

Or my original analysis for the spectrum mess here. https://support.mozilla.org/en-US/questions/1275339#answer-1276614

Perhaps it is time for them to lift their game and actually fix some of this stuff. Or is it their support is just that bad. I don't know.