Below are some links showing you how to install an HTML email signature in various email clients:

 

For Gmail on iOS devices (iPhones/iPads), as long as it’s properly installed in Gmail on the web (per above instructions), just make sure that “mobile signature” is turned off in the Gmail app on your iPhone/iPad by going to Settings > Signature Settings > un-tick “Mobile Signature”

It won’t show up when you’re composing a message on your phone, but it will pull your signature from where you originally installed it in Gmail and send it along with your message.

 
 
Outlook on a Mac (OSx): https://youtu.be/nTJAkljxd30
 
Outlook Web App (OWA): https://youtu.be/Eu0R0gM9zlk
 
Outlook Mobile App (iOS/iPhones/iPads only): https://youtu.be/SbU51liJKiA
 
Apple Mail:
 
 
iOS (iPhones/iPads) – https://youtu.be/uWW2PlUMuko
 
 
 
 
GoDaddy Workspace: https://youtu.be/J93hpNg3WEE
 
 
Third-Party Mobile Apps:
 
Spark Mail (iOS/Android) – https://youtu.be/w3-AQcnsEB0
 
Aqua Mail (Android only) – https://www.youtube.com/watch?v=7tBi2_VdnNA