Hey if they're free.....
Other idea is... maybe check and compare the small details in the seperate emails. It might be something like....
"Thanks for your order, your package will be shipped out at 8 am on Monday 11/7 2010"
"Thanks for your order, your package will be shipped out at 9 am on Monday 11/7 2012"
"Thanks for your order, your package will be shipped out at 9 am on Tuesday 11/7 2013"
"Thanks for your order, your package has been shipped out at 9 am on Monday 11/7 2013"
"Thanks for your order, your package has been shipped out at 8 am on Monday 11/7 2012"
"Thanks for your order, your package has been shipped out at 9 am on Tuesday 11/7 2010"
"Thanks for your order, Ted will no longer be processing your orders."