Hopefully not, only the unregistered version of MaxBulk Mailer adds a piece of text stating the version used has not been registered yet. This is to prevent using the software for real jobs without having purchased a license first.
The text looks like the following on 'Plain Text' messages:
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This email has been sent with an unregistered version of MaxBulk Mailer
MaxBulk Mailer is a new easy-to-use mail merge software for Mac/Windows