Content rule for content with expiration date

Hello everybody,

I´m new to plone and tried to solve the following problem by using a content rule:
For folders with an expiration date an email should be sent 3 month before expiration.

In my opinion there is no matching trigger for this. The condition would have to be a TALES expression and the action send mail. Has anyone out there experience on this and can help? Is it possible at all to solve this with content rules or is there another way to handle this?

Thanks a lot! I´ll try this.

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