To install Email Signature in Gmail for iPhone/Android, please follow the following steps:

  1. Firstly, install the signature in Gmail web.
  2. In your Gmail app, make sure mobile signature is turned off. To turn it off go to Settings > Select your mail account > Signature Settings > Switch Signature to Off
  3. Wait for 4 hours for the web-based Gmail server to sync with your mobile device's Gmail app.
  4. Your signature will not show up when you compose a new email but it will be added to your email after you send it. 

Good job, you! Send a test email to yourself to make sure it works.

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