In order to remove the default formatting in Outlook, you update your HTML source and take control of the formatting:
Change from:
((Mobile))
Change to:
- This example assume Arial 10pt black font.
- Notice how both HREF and FONT are now styled by your custom HTML.
<a href="tel:((Mobile))"> <font color="#888888" face="Arial, Helvetica, Geneva, Sans-Serif" style="FONT-SIZE: 10pt; text-decoration: none; pointer-events: none;">((Mobile))</font> </a>
On some devices an underline will show, but it's not clickable and the Skype logo will no longer appear.