Guide for Styles
To find out what works and doesn't work in each email client, read this handy guide from Campaign Monitor: https://www.campaignmonitor.com/css/
HTML for Outlook 2016
Preventing text from wrapping
Text can wrap when viewed on a smaller screen. In this example the phone number label is on one line, and the phone number has wrapped to the line below.
To keep the phone label with the phone number use a span with a style of <span style="white-space: nowrap;"> P: +64 9 303 2222</span>
This link will show you how to make phone numbers keep their style without reverting to blue underlined links: Phone Styles Phone Styles
Horizontal Rules (HR tags)
It is possible to use horizontal rules in your signature, and to apply your styles to them.
Here is an example of code to produce a thin, red line:
<hr color="red" noshade="noshade" style="width:100%;display:inline-block;vertical-align:middle;border-top: 1px solid red;border-bottom:none;" />
See this guide on styling them: https://www.w3schools.com/Tags/tag_hr.asp