My post yesterday about the use of images in email got me thinking about what the best days or times are for doing bulk email sends. There really isn’t one answer, as each list is unique and finding the best times is a matter of trial and error. But I’ll take a shot at providing some general guidelines.

Based on my own experiences and everything I’ve read, for business to business emails (or any list that consists mostly of work addresses) the best days are Tuesday, Wednesday and Thursday.

The rationale for this is pretty simple. Most people don’t check their business email accounts on Saturdays or Sundays. On Mondays people tend to be in heavy delete mode, as they try to clear all the email that has accumulated over the weekend. On Fridays, people tend to be less focused, as they look forward to the weekend. Friday is also an extremely popular day of the week to take off, meaning your email could end up not being seen until Monday.

In terms of time for business-focused email, it is best to send email out during normal business hours. If you send your email before or after work hours, there is a good chance folks won’t see the email as they try to clear their email queue first thing in the morning and go into delete mode. Assuming you are trying to reach a US audience, I think between 12:00 and 4:00 EST is the best time, as you’ll catch people at work in all time zones.

For business to consumer emails (or any list made up mostly of personal email accounts), the situation is more fluid. Some studies show that these audiences tend to be more responsive to emails sent after work hours and on Fridays and weekends, as this is when people tend to check personal email accounts.

It makes sense – lots of people with desk jobs might not check their personal email accounts during the day and others don’t even really use email in their jobs. Just as importantly, business to consumer email tends to be about action. You want users to buy something or enter your contest or whatever. Most people are more comfortable performing those type of activities on their personal computers during their off hours.

My sense though is that there is more room for error for business to consumer emails in terms of time/date. In my experience, volume to personal accounts is lower and spam tends to be less of a problem. So I don’t think people get as delete happy as they do with their corporate email accounts.

Ultimately though, every list is different. Email Labs suggests looking at when people register for your list and trying to send during the days/time you get the most sign ups. But the best way to figure out when to send is through trial and error. Try sending out messages on different days at different times and see when you get the best open and click through rates. This will allow you to figure out your own best practices for your list.