html signature

This is not a Dreamweaver question.  Therefore, there is no answer to this in DW.

I think @Ben107584 M gave you good advice.  Use an online signature generator that specifically targets your preferred email platform. 

I have used this one with success on the major online platforms.  It works with HubSpot, Gmail, Outlook, Apple Mail, Yahoo Mail, and more.

• https://www.hubspot.com/email-signature-generator

This one offers a choice of email platforms including Outlook 365.

• https://www.mail-signatures.com/signature-generator/
• https://www.mail-signatures.com/signature-generator/manual/#supported-clients

That said, I don't think it's possible to create 1 HTML email signature that works equally in all platforms -- unless you use an image but that has its own set of problems.

Good luck!

Outlook on the Mac uses a different rendering engine then Outlook does on Windows, they are by no means the same program, not to mention the Office teams at Microsoft have always been historically separate and do not always develop the same feature sets across platforms.  So basically if you are using anything more than tables, the display will most likely break in Outlook.  There are also platforms that can help you dynamically implement HTML signatures across your organization like Terminus (formerly Sigstr), Opensense, Templafy, etc. just to name a few.  That might be something you want to consider as well.

The answer is in the code, code that we are presently not privvy to.