How do I get rid of "MAILTO" and brackets around email addresses?

I have been using Outlook 2007 for years, and recently it started this odd thing where in emails, email addresses show up in an inconvenient way. Instead of looking like this:

From: username@domain.com

They look like this:

From: Name, User [mailto:username@domaink.com]

There are two problems with that. First, if I want to reply to that email address so I click [mailto:username@domaink.com], it opens up a new email with the email address as mailto:username@domaink.com which is invalid so I have to manually edit it to take out the "mailto: part. Second, if I want to quickly copy the email address, it's very difficult to highlight it for copying without either inadvertently clicking the email address (which opens a new email) or copying the right bracket, which of course invalidates the email address.

I want to set up Outlook to stop doing this, can someone please tell me how? Or at least tell me what to search for in Help, because I'm not finding anything. Thanks!