If you take a look at the source code for the very first e-mail, under the alert tag it has the line "March has 32 days". This is the title of the last story in the Mystery Tales #40 Comic book. Coincidentally, this exact issue was featured in the season 4 episode "Cabin Fever", which inspired a couple fans to order the issue online. The following scans are from their blog where they uploaded scans of each story:
The story is about an architect named John Billings, who relives March 31st and stops a bridge from collapsing. According to Wikipedia John Billings was a famous Australian fertility doctor.