(imported from commit 68607b015c640529d4d65065ace82a18d57610a3)
The queued email gets deleted if the user signs up before it gets sent. Otherwise, they are reminded in 2 days that they still haven't signed up. This addressses Trac #1812 (imported from commit c1bdc09c03ac576b08986e56994de72d52fd293b)