Not sure what you mean, because you appear to be talking about the (in)ability to see or save sent messages, not about the ability to receive messages…

What type of account is this (POP, IMAP)? Which is your email provider? And what is your problem exactly?

And please post a screenshot or properly quote any error messages you get so we may figure what are you talking about.

I could send and receive emails this morning, last email received was at 11:38. at 12:30 I could not receive emails on my desk top computer. I can send and receive on my phone without issue I can send emails. It does show an error message Your message was sent but a copy was not placed in your sent folder due to network or file access errors I does show its connecting to the server but shows no messages to download Windows 11 did update overnight which could be the cause I have had the same problem in the past but when I closed Thunderbird and reopen a confirm security exemption popped up and once confirmed everything worked. I am not getting the security pop up this time IMAP siteground is the server

OK, so the problem is that Thunderbird fails to save on the server a copy of the messages you send with it…

This problem is typically caused by Thunderbird trying to save sent messages in a Sent folder that doesn't exist on the server and which Thunderbird won't try to create automatically either. You might solve that problem by manually creating the Sent folder yourself, but a folder for that purpose with a different name such as Sent Items may already exist on the server, in which case the right way to solve the problem is by telling Thunderbird to save sent messages in that folder instead.

Go to Account Settings > Copies & Folders. Under When sending messages, select Other. Then, amongst the options available there, look for a folder with a name that would indicate it's meant to save sent messages (e.g. Sent Items or similar). Choosing that folder should solve the problem.

The main problem is that I can not receive emails on my desk top not that it will not save to the sent folder

Aaaand… The "security exemption" error you mention would be an indication that this account isn't configured properly. In particular, you appear to be using a wrong hostname for the mail server. You shouldn't have had to create a security exception for that, something is amiss there. It would help if you post a screenshot of your account server settings (without revealing any passwords) in order to be able to see what you did wrong.

Why would it work for 5 years then not work. What settings do you want to see? Server is us143.siteground.us port is 993

outgoing post is 465

The part of Account Settings > Server Settings at the top of the pane up to and including the security settings, i.e. what you would have to specify if you had to manually set up this account anew. I don't need to know the part of the username to the left of the '@' if you're using your full email address for the username, but I may need to know the part to the right (i.e. the domain of your email address).

Well, looks like I won't be able to figure which should be the mail server names that you appear to not have configured properly. Seems only you can do that using (I think) the manual procedure described here:

https://world.siteground.com/kb/how_to_configure_my_mail_client/

Problem solved. Site ground changed the server name without letting some clients know