Various studies have been conducted just to determine which day of the week and time is best for sending out email newsletters to maximize open and click-through rates. Unfortunately, it is very tough to nail down the best day and time due to differences between the types of audiences that are reading the emails. Obviously email newsletters targeting business recipients will require a different timing as opposed to those being received by consumers.
Sending newsletters to businesses
Consider the fact that some companies would like their staff to have more work-life balance and discourages their employees from reading business emails after working hours. This means your email should ideally reach your recipients during their working days (Mon to Fri) and working hours (9am to 5pm).
Best time would be to send out your emails before they start work. Sending out the emails at 8am on a weekday will give your recipients time to scan your email before they actually start work. During this time, some might be taking their coffee or breakfast and thus have some spare time to read whatever you might be sending them.
Sending newsletters to consumers
Dealing with consumers gives you more flexibility since your audience could be working, stay-at-home folks, students, etc. To this end, you will need to know your audience better. If you want to maximize open and click-through rates for this group in general, it is best to send in the evening.
The logic being both the workers and students would be home by then and be able to read the emails after they have had their dinners. For the stay-at-home folks, they probably have other duties to attend to during the day so evening works for them too.
Avoid sending emails on weekends and Fridays as most people will be busy with their social lives and won’t have time to read your emails.
Adjust your sending schedule to what works best in your case
The above is a very general idea on how to determine the best day and time to send out email newsletters. Ultimately, you will have to keep changing your sending schedule until you achieve optimal open & click-through rates.