Missing HTML Signature in Emails Sent from Mail (Apple) or Thunderbird

Condition

Emails sent from Thunderbird or Mail (Apple) do not attach the HTML signature, but the plain signature. If you have not specified a signature for plain text, the email will be sent without a signature.

Reason

Some email clients such as Mail (Apple) and Thunderbird send emails by default as plain text and not in HTML format. Thus, the plain template is loaded in the Signature and Disclaimer.

Remedy for Mail (Apple) on MacOS

See Using plain or rich text in emails in Mail on Mac and follow the instructions of the manufacturer.

Workaround for Mail (Apple) on iOS

Format one or more characters bold, italic or underlined in your email text.

The client sends the email in HTML format and Signature and Disclaimer attaches the HTML signature.

Remedy for Thunderbird

  • For single emails: Select Write > Options > Delivery Format > Rich Text (HTML) Only.
    Figure 1: Options for a single email
  • For all emails: Select Write > Tools > Account Settings > Composition & Addressing and activate Compose messages in HTML format.
    Figure 2: Settings for all emails