If you wish to remove the underline from all links in your message, this can easily be done using the Default Fonts Feature.
Looking to remove the underline from just one specific link? Please see Remove the Underline From a Specific Link.
- Edit the message in question.
- Select the Design tab on the right.
- Scroll down to the Default Fonts section.
- Unselect the Underline option for Links.
As you can see above you also have the ability of formatting all links in your message as a certain colour, bold, italic or removing the underline.