A new index from delivery consultant Return Path backs up research we reported last week claiming Monday email gets the best open and click rates.

Return Path`s own analysis of 3.4 million messages showed email sent on Monday is more likely to get where you want it to go, and mornings between 6 and 10 ET are the best times of all.

That`s when delivery rates are 2% better than normal. From 10 a.m. to 2 p.m., delivery rates fall 3%. Weekends between 10 a.m. and 2 p.m. ET are the worst, with delivery rates falling 9.5% to 10% below normal.

Why the variance? Mainly in the way ISPs manage bulk email and spam-control measures, such as limiting how many emails from a single address the ISP will allow through at one time and how it tunes its spam filters at different times.

Return Path`s conclusions:
-- Mail on weekdays, not weekends. Delivery rates on the weekends are generally lower and fluctuate more
widely than delivery rates for campaigns sent on weekdays.
-- If you have to send on a weekend, do it 6-10 a.m. ET or 10 p.m. – 2 a.m. ET.
-- Email campaigns sent 6-10 a.m. ET have higher delivery rates than any other time period no matter which day.
-- Monday delivery rates are highest overall, followed by Tuesday, Thursday, and Wednesday.

See the research reported in EmailSherpa here: http://www.marketingsherpa.com/sample.cfm?contentID=2770