From Phil Butcher:

Email now works and the period specified online is correct (tomorrow) but the grace period in the email below is still showing from the 'start of MS time'.

Also might
"This attempt is now overdue. It should already have been submitted. If you would like this quiz to be graded, you must submit it by Tuesday, 1 May 2012, 11:40 AM. If you not submit it by then, no marks from this attempt will be counted."

Be better as (note the missing 'do' too)
"'iCMA01 - email check' closed at <date/time> and this attempt is now overdue. If you would like this quiz to be graded, you must submit it by Tuesday, 1 May 2012, 11:40 AM. If you do not submit it by then, no marks from this attempt will be counted."