• 6AM to 10AM: The second most prevalent email opening time is at the the beginning of the working day.
• 10AM to Noon: Consumers are not opening marketing emails, choosing instead to focus on work.
• Noon to 2PM: Consumers are unlikely to open emails during their lunch break, choosing instead to spend their time on news and magazine alerts.
• 2PM to 3PM: Right after lunch consumers remain focused on work, responding mostly to email offers related to financial services.
• 3PM to 5PM: Consumers start thinking about their personal situation and as a result, more emails relating to property and financial services are opened during this time period than any other.
• 5PM to 7PM: Consumers tend to open business to business (B2B) promotions during this period, but also open more holiday-type promotions during this period than any other.
• 7PM to 10PM: The time period when recipients are most likely to respond to consumer promotions is when they get off work.
• 10PM to 6AM: This is an email dead zone, as most sent during this period are ineffective.

Here are a few other timing issues to consider:

• Bounce rates are highest in the morning.
• Open rates are highest during the weekend by 45%.
• Open rates are 53% higher in the morning.
• Click rates are 10% higher on the weekend and early morning.
• The most effective sending frequency is 1 to 4 per month.
• Conversely, the unsubscribe rate is higher at 1 to 4 per month, but levels off at 8 to 31 per month.
• The highest unsubscription rate occurs among those who have been subscribers for less than 10 days.
• The highest click-through-rate (CTR) is with those who have been subscribers for less than 10 days.

Read more: http://music3point0.blogspot.com/2012/01/science-of-email-timing.html#ixzz1ksImNoC9 Under Creative Commons License: Attribution Non-Commercial Share Alike