Placeholders used to always work whenever pasted into an email message.
Mailbutler removed this functionality in a recent update so the only way a placeholder works is by manually using Mailbutler's placeholder insert process which takes several extra clicks.
Mailbutler has removed automation and convenience from a plugin whose entire purpose is to improve automation and convenience.
Please put the original functionality back so we can simply paste in placeholders or messages and have the placeholders work like they always did.