When you create a link it will automatically become underlined.
This can easily be removed in the HTML.
Underlined Link
If you don't want your link to be underlined, you will need to change this in the HTML code of the email.
Switch to HTML view
Switch to the HTML view using the option at the bottom of the editor.
Finding your link
1. Using CTRL+F find your link text, (in this example it is Visit our Website) within the HTML code.
The beginning of a link will look something like this:
<A href="{CONTENT lz.aspx?p1='{Content/EMailLink}{Content/CampaignCode}&w=8177&cID=0&cValue=1" CampaignURL} ?>Visit our Website</A>
2. You will need to enter the following code (in red) into the link so it looks like this:
<A style="TEXT-DECORATION: none" href="{CONTENT lz.aspx?p1='{Content/EMailLink}{Content/CampaignCode}&w=8177&cID=0&cValue=1" CampaignURL} ?>Visit our Website</A>
Edited Link
Your edited link will look something like this.
Switch back to Design View
Switch back to design view to check that your underline has now been removed.