Plain text signatures are used when replying emails in plain text. Thus, only create plain text signatures used as reply/forward.

Note: Images are not supported in TXT format.

Open the admin console > Signatures:

  1. Select Plain Text from the drop-down (TXT format is automatically generated). 
  2. Adjust and click Preview, select Plain text signature.
  3. Close the window and save the changes when you are happy with the result.