Please provide the error message text you receive when this failure occurs. For both incoming and outgoing, please.

The web based e-mail client (webmail), does not access e-mail the same way that regular e-mail clients/programs like Thunderbird does. So the problem could be with the Verizon servers. First we need to know what the actual error is, though.

TB doesn't give an error message on the incoming side, the progress bar at the bottom continues until it times out. If one tries to send an outgoing message it just says that it is unable to send. It doesn't appear to be an internet problem per se because one can still access web pages while this is happening. Also, the Verizon web based email client works and can be accessed while TB can't.

Please post a screenshot here of the "Mail and News Accounts" section of Troubleshooting Information:

Thunderbird menu: Help: Troubleshooting Information

Here's the error message. So it would be nice to ascribe the error to Verizon's servers but I can still log on to their web based email client.

As I said, how webmail deals with e-mail is different from how an e-mail program like Thunderbird does. They use different servers.

Your error message essentially says that Thunderbird connected to the server "smtp.verizon.net", but when it tried to send the e-mail, the server didn't respond for a long time, so Thunderbird gave up.

So "smtp.verizon.net" is not responding properly, but Verizon's webmail doesn't use this server to send e-mail.

Please do provide the information I asked for.

My bad, I thought you wanted the error message rather than the troubleshooting information. Please see the screenshot below and thank you.

Try testing a new Thunderbird Profile to see if the same thing happens.

Hold down the Windows key and press R.

In the run box, type:

thunderbird.exe -p

This will start the Profile Manager for Thunderbird. Click the "Create Profile" button.

Type in a new profile name. Don't name it "default" or "Default User". Use your imagination.

You can let the Profile Manager create the new profile in the default location, or you can click the "Choose Folder" button to choose where to set up the new profile. I personally put my profile folders where I want them, so it is easier for me to back them up.

After you click "Finish" select the new profile in Profile Manager, un-check "Use the selected profile without asking at startup". Then click "Start Thunderbird".

Thunderbird will now start with nothing set yet.

Setup your e-mail, then test sending & receiving to see if things work better in this profile. If it does, then you can copy your data from the old profile to the new: Create a clean new profile in Thunderbird and import your stuff from the old profile

Excellent suggestion though when I tried to create the new profile and set up the email account, it wouldn't connect to the server. Verizon denies a problem on their end.

Check the security on all the devices that are using your Internet connection. Make sure the antivirus and firewalls are working and up-to-date.

Run scans with additional anti-spyware and anti-malware scanners. I recommend using the free versions of both Spybot Search & Destroy and Malwarebytes Anti-Malware.

Check to make sure that the WiFi you are using is protected by a password.

Make sure no one using your Internet Connection is sending spam. Know who is using your Internet Connection.

If/when you clear all that:

Backup your Thunderbird Profile folder to another location for safekeeping.

Uninstall Thunderbird. Reboot computer.

Run Disk Cleanup for your C: drive (type "disk cleanup" into Cortana search, then click on it in the search results).

Reboot the computer again.

Download and install Thunderbird again.

Create a new Thunderbird Profile and configure your e-mail account in it.

If there is still a problem connecting to the Verizon server, then the problem is definitely with Verizon, no matter what they say.

If the problem was not intermittent, but constant, then I would suggest checking your hosts file for rogue entries to do with the Verizon e-mail servers.

I think it is Verizon and they have finally confirmed that the web based email client and the email servers are different though they deny any server issues. It happens nearly every afternoon and evening and now has effected all of our accounts. Is anyone else experiencing these problems?

Given the timing (afternoon and evening when Internet usage is highest), then I'm guessing the mail servers are overloaded. The servers are not able to keep up with the demand.

To learn if other Verizon customers are having this problem, I suggest checking out the Verizon Forums, or search the Internet for other forums where people might talk about Verizon.

I've helped as much as I can with Thunderbird and Windows instructions that could help you, even though I'm convinced this is a problem with Verizon servers.

I'm done.

Now, I've seemed to link the difficulty to the time that I launch a VPN on my system to deal with work applications. After logging out of the VPN, TB fails to be able to connect with the Verizon server to send or receive emails. Thoughts?

Check the proxy setting in Thunderbird.

Thunderbird menu: Tools: Options: Advanced: Network & Disk Space tab

If you are not using a proxy, select "No proxy". If you are using a proxy, set it manually.

If it is set to "Auto-detect" or "system proxy settings", then maybe when you start or stop using the VPN, Thunderbird uses the wrong proxy settings.