This plugin adds a configurable signature to all outgoing emails from your WordPress site.

I have a mail which is not having the signature appended. Why not?

This probably means that the plugin sending the mail is using its own mechanism to send it, instead of calling wp_mail as it should. Request the plugin author to instead use WordPress's official mechanism.

The signature is only being added to the plain text of an email, and not inside an HTML mail

That's right. If you have some code that's capable of delving inside the HTML to do this correctly, then I'll be pleased to use it. But I couldn't think of a way.

1.0.4 02/Jun/2016

• TWEAK: Minor clean-up

1.0.3 12/03/2012

• Added links to other useful WordPress resources

1.0.2 11/19/2012

• Added a screenshot

1.0.1 11/13/2012

• Fixed a typo

1.0 10/29/2012

• First version

Standard WordPress plugin installation:

1. Upload add-email-signature/ into wp-content/plugins/ (or use the built-in installers)
2. Activate the plugin via the 'Plugins' menu.
3. Go to the 'Add Email Signature' option under 'Settings'.
4. Follow the instructions.

Configuring a signature