Outlook 2016 HTML Signature
Outlook works best with a restricted version of HTML for the signature, so if you can't use the webmail signature generator and copy / paste that into your Mac Outlook - look for a third party tool to assist.

One that works well is this utility from the App Store. It fixes the problem with Outlook breaking HTML signature. Costs about USD 3 though but for me it's worth it.

HTML Email Signature for Outlook - Daniel Caspi