is there some sort of error message that we might use as a clue?

We only know what you tell us. So far that is enough to suggest this support article. https://support.mozilla.org/en-US/kb/cannot-send-messages

Technician said that we have virus and this is the reason we can't sent emails.

Hello there We have read the message We try to help

If your e-mail program has a virus ,it is better to avoid it to get help via the internet, the combination of visiting links and having a virus on your system is not really useful, this call of links are infected or you infect them with your approach.

Greetings Firefox volunteer

I just need to know why its not sending email. It seems like email is blocked. Why cant tech support check it? I need to solve this problem as soon as possible. I here not to post questions agai and again weeks by weeks. Just help me to resolve issue.

You were asked earlier to post any error messages, yet you have not. You tell us absolutely nothing, yet expect help.

Hello there

Some time ago there were attempts to get certain figures who disguised themselves. Impersonating Thunderbird mozilla and Google and also others try to enter your system and spread a virus, usually a ransomware alert is issued.

These actions that should be performed are the downloads that are not real. Download Thunderbird from a trusted site.

https://www.thunderbird.net/en-US/thunderbird/releases/

Greetings Firefox volunteer.

Hello there

If your system contains a virus wait for help from these you mentioned. Apparently, your antivirus shield has your clients, for example. excluded from the activities until it is resolved.

Greetings Firefox volunteer