I can't receive or send emails in thunderbird.

Ports 587 and 465 are both used for secure email submission (SMTP), but they handle encryption differently. Port 587 uses explicit TLS (STARTTLS), starting unencrypted before upgrading. Port 465 uses implicit TLS, encrypting the connection from the very beginning. Port 587 is the modern standard, while port 465 is a legacy option.

What antivirus are you using? Many third party antivirus product cause sending mail timeouts, especially if large attachments are included.

Over the years I have also seen many issues with email servers and the use of VPN's. Do you have one?

I am using Microsoft Defender only. Norton VPN is installed but disconnected. I have no third-party antivirus running. Thunderbird's SMTP connection to mobile.charter.net intermittently times out, while Windows Test-NetConnection mobile.charter.net -Port 587 consistently returns True. Spectrum webmail works, and Thunderbird can sometimes send successfully before timing out again.

Hello there

Please try booting your Windows PC into Safe Mode and launching Thunderbird from there. If you can send emails and your SMTP settings are correct, the issue is likely caused by the Norton VPN rather than the entire antivirus suite. To ensure your SMTP configuration is fully accurate, please verify your settings with us first. Additionally, you could try increasing the TCP timeout limit?

https://support.mozilla.org/en-US/kb/cannot-send-messages

https://support.mozilla.org/en-US/kb/cannot-receive-messages

Hello there

If the Norton VPN browser extension or app / add-on is causing this bottleneck, it likely stems from the factors we discussed. Mail servers trigger alerts when detecting sudden login anomalies—such as a connection abruptly jumping from your physical location to a remote VPN endpoint.

While the ports used by Thunderbird remain functional, they are subject to strict VPN routing policies. Furthermore, automated anti-abuse systems at major data centers and mail providers frequently block known VPN IP addresses to mitigate malicious traffic or unexpected connection spikes.

Hello there

If you want to try using the TCP timeout method, you can certainly do so. In Thunderbird, go to the Settings menu, scroll all the way down to the bottom of the General panel, and click on Config Editor in the search section.

Paste the following text there: mailnews.tcptimeout. Click the Pencil (edit icon) next to the value; the default is normally 100. Change this value to 600, which will increase the timeout period to 600 seconds. This equals a 10-minute timeout limit. Finally, click the Save option.

Tip Older Spectrum accounts sometimes run slowly with Thunderbird, which can cause server issues. You should check for an update to fix the problem.

Issues with sending or receiving emails are sometimes caused by outdated Spectrum software blocking server settings.

This is often difficult to detect during normal use of standard email clients.Therefore, we would like to review your SMTP settings to check how they are configured for both Spectrum and Thunderbird.

Could you please send us screenshots of these settings?You can usually find these settings within your email client under 'Account Settings' or 'Server Settings' for outgoing mail (SMTP).

Question What did Spectrum offer you at your last contact with them? Did they give you security updates or software enforcement?

Greetings, I'll be out of town for the next few days. We'll continue these diagnostics upon my return if that works for you. Thanks, Mike.