Hi rogergr311049, do you mean links in your email in Firefox, or links in a separate email program on your system?

Firefox has three different preferences for whether to divert tabs destined for a new window to a new tab instead. Only one of these has a checkbox. I'm going to list all of their details and insert a bold note for the change I suggest trying under (B):

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(2) In the search box in the page, type or paste neww and pause while the list is filtered

(3) Review/Adjust the preferences as follows:

(A) browser.link.open_newwindow - for links in Firefox tabs

This is the one that has a checkbox on the Preferences page:

• 3 = divert new window to a new tab (default) <== keep this
• 2 = allow link to open a new window
• 1 = force new window into same tab

(B) browse.link.open_newwindow.restriction - for links in Firefox tabs

By default, if a page sets width, height, or toolbars for a popup, Firefox will let it be a separate window. To force those into a tab as well, you can change this preference to 0:

• 0 = apply the setting under (A) to ALL new windows (even script windows with features) <== try this
• 2 = apply the setting under (A) to normal windows, but NOT to script windows with features (default)
• 1 = override the setting under (A) and always use new windows

(C) browser.link.open_newwindow.override.external - for links in other programs

• -1 = apply the setting under (A) to external links (default) <== keep this or try (3)
• 3 = open external links in a new tab in the last active window
• 2 = open external links in a new window
• 1 = open external links in the last active tab replacing the current page

To return to normal if things go haywire, there's an arrow-like reset button at the right end of each of those rows if it has a non-default value.

Success?

Absolute success !!!!!

That's it, although it's a little complicate to find out by yourself all this process !!!

But that's Life !!! You can't only get, but you have also to give. In this case you give a little piece of mind and you get the BEST and FIRST Internet Browser :

MOZILLA FIREFOX !!!!!!!

Thank's a lot JOHN HATZITOLIOS