I'd suggest leaving a bug report on the CPAN RT System. That's the safest way of letting Dave know he should update his key.

According to the module's documentation, the urls are:

http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DateTime%3A%3AFormat%3A%3AMail
mailto:bug-datetime-format-mail@rt.cpan.org

In reply to Re: DateTime::Format::Mail signature check fails by rhesa
in thread DateTime::Format::Mail signature check fails by Anonymous Monk

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