The best time to send an email newsletter depends on a number of things. Firstly it depends on whether you are sending to consumers or businesses.
If you are sending to businesses the best time to send an email newsletter is when the recipient’s inbox is less full and they are not snowed under. This pretty much excludes Monday mornings, when sifting through emails is a major chore for most people. A marketing campaign rarely hits the spot when there are lots of urgent messages from colleagues in the reader’s inbox.
Equally sending on a Friday afternoon may mean that anyone who knocks off early or just winds down a bit on a Friday will ignore your amazing offer till Monday when the paragraph above applies.
If you are sending to the general public (consumers rather than businesses) the best time to send an email newsletter is when they are ready to act. Mid-evening can be an excellent time, as can Saturday mornings.
However, if your target market is older than average, they may not be as receptive to messages at the same time of day as younger people.
The only really effective rule is to test an idea and retest. Split your mailing list into groups and send at different times of the day and days of the week.
Once you have your results, analyse them to see if there is a statistically significant difference in response depending on the dates and times sent. Start with basic principles and refine each time you test to see if the time makes a difference, or split a single campaign into lots of little groups and send them out at intervals.
Obviously you will need to track which times produced the best response rates, so don’t forget your tracking.