The church will collect used stamps for the Leprosy Mission of Canada. Used stamps can be sold and the money used to help stamp out Leprosy.
You can bring any mail with a used stamp on it to the church or give to any member of the church.
If you want to just bring the stamp cut it from the envelop leaving at least a quarter inch border around it. Don’t try to remove it from the envelope.
More information is available at https://effecthope.org/res/pub/Stamp-Program/Stamp-Brochure-WEB2.pdf