Guess the first thing is Mozilla Thunderbird thinks the email is a scam to begin with.
In the email, the link displays like this:
Since you have recently changed your email, we require that you verify your new email address. You will only need to click on the link once, and your account will be updated.
To complete reverification, please visit the following link: http://www.modthesims.info/register.php?a=act&u=x&i=x
I removed the numbers just in case of security issues. Anyway, so you hover over the link and that's not where it goes, it goes to this link:
I don't recommend trying that link. I'm not sure what's gotten into your system but this same pair of displayed link and alternate actual target appears four times in the email, and it looks kinda unprofessional so I'm not going to either link.
If anyone wants the email, I can forward it where you want. I'll hold on to it for a few days.