I use Thunderbird at work, as I cant stand outlook. However one person in particular does not receive my emails.

I tried using outlook and the email went through, and through the webmail and it went through. So it seems it is an isolated problem with Thurnderbird and nothing to do with the outgoing server.

Also sometimes but not often the emails go through.

What could the problem be? any ideas?

Im not to tech savvy so basic terms please..

No idea.

Are you using HTML formatted mails or plain text?

For this one person I have specified plain text.

The only time I ever have problems with Thunderbird is when the outgoing server port somehow gets mysteriously changed and since I am an AOL user this means that mail doesn't get sent. Try checking your ports would be my best guess.

If using plain text you should be fine.

As the above poster suggested you should check that the SMTP is set correctly. If you are using a SMTP server not provided by your ISP you should shouldn't be using port 25 as it sometimes gets blocked.

Only the admin of your SMTP server can give you a valid port besides 25.