Cannot send email to myself

Can you use the internet otherwise when connected via the router ?

Who is your mail provider, and what program are you using to send email?

My Internet provider is Optimum, and yes I can access the Internet, receive & send email but not to my wife email.
We are using window mail and thunderbird, Vista window

If your e-mail provider has a webmail option (i.e. you just go to their e-mail home site via the internet and sign in, compose and send) try that instead of using an offline reader like Thunderbird.

If that works it suggests that the settings are wrong in Thunderbird.

it sounds like your router is blocking ports. If the program settings were wrong, it wouldn't matter if you had the router connected or not.

Linksys support accessed my computer and tried change the setting of the router but they failed to make it work. They concluded that it is a hardware problem with the router and I bought new one hoping it will fix the problem. I guess the routers start acting when I connected the router to the backup UPC I bought recently.