Correction: (Number of emails in release / 12) * (Your birth month -1 ) and ending with (Number of emails in release / 12) * (Your birth month)
Examples:
1200 emails
Born in January
(1200 / 12) * 0 = 0
(1200 / 10) * 1 = 120
You are responsible to read the first 120 emails
1200 emails
Born in April
(1200 / 12) * 3 = 360
(1200 / 10) * 4 = 480
You are responsible to read emails 360 through 480