Signature not showing in HTML form in Email notification mails from CP. After saving text with the option selected as "Send the message as HTML", it messed up the email contents by merging all of sentences to one line.
Incorrect HTML markup.
Create Email message according HTML markup rules (use HTML tags etc). If you just choose "Send the message as HTML" the message will not be automatically rebuilt as HTML like in MS Outlook. All plain text will be merged to one line according HTML markup rules.