How's Monday for you? According to a new study by email marketing firm eROI (released exclusively today to MarketingSherpa), Monday might actually be the best day to send marketing email, even though Tuesday and Wednesday are now the prime days.

eROI studied results from more than 7.7 million commercial messages sent over 30-days by more than 6,000 marketers from a wide range of industries. The result? Currently email recipients actually open and click a lot more on Monday.

"Monday is coming across as the clear leader even though it has the lowest volume of the work week, because recipients are more likely to read their email," eROI email analyst Jeff Mills says.

Email fatigue also hasn't set in yet on the first workday of the week, he adds. "People appear to be less bothered by this lower volume of email. Work hasn't really piled up for the week yet, so they have the time to read and respond."

As the week wears on, eROI President/CEO Ryan Buchanan says, "we start to see significant drop-offs in (opens) and clicks. People probably are not capturing their audience's time as effectively."

Here's more results data, plus a link to charts and graphs... (Note: Unless specified as Pacific Time, times of day were generalized to reflect whatever time zone the recipient is in.)

Monday: Low Send, High Open and Click:

-- 8% of all email sent Sunday-Saturday goes out on Monday, with most of it going out between 6 a.m. and 1 p.m. Pacific time. Tuesday and Wednesday together account for 54.5 percent of all email sent weekly.

-- But, 35.5% of all email sent on Monday gets opened. That's actually the second-highest result of the week (Saturday was tops at 38.2%, but the study discounted it because the email volume was so low compared to all other days in the week.)

-- And, email sent on Mondays collected an aggregated 5.9% click rate, the highest of any day in the week (4.4% on Friday came in second).

-- Monday also tied with Thursday as having the lowest unsubscribe rate, at 0.1% each. (Saturday led at a statistically significant different of 0.3%).

-- Monday also exerts a carryover effect: Recipients are carrying over Monday email to open on Tuesday (see next entry).

Tuesday: It's Got Legs

-- Although the 25% open rate is the week's second-lowest (excluding Saturday-Sunday), recipients open mail earlier in the day, creating the carryover effect of Monday mail.

"Tuesday has longer legs," Mills says. "Tuesdays have pretty high open rates for about four hours from 9 to noon Pacific time."

Even if they don't open their Monday email on Monday, they're carrying it over and opening it early Tuesday instead of deleting it without opening, he says.

-- 28.6% of commercial email goes out on Tuesday, the single busiest day in the week.

-- 25% of that email gets opened, third-lowest for the week.

-- Tuesday collected the highest number of clicks on average -- 77,720, followed by 60,554 on Wednesday -- but it recorded a 3.4% click rate, third-highest for the week.

-- Noon was the peak hour for sending email. For every other day of the week, 9 a.m. was the peak hour

Wednesday: Hump-Day Slump

-- The email torrent is starting to slack off a bit, but a quarter of all commercial email still goes out that day.

-- Email also has the widest range of sending times on Wednesday, from just after midnight PT to mid-evening.

In contrast, email goes out earlier in the day on Tuesday. On Monday, it's concentrated in a narrow band from 6 a.m. to 1 p.m. PT, and a secondary spurt in late evening.

-- Email fatigue starts to set in on Wednesday, too. The day's 22% open rate is the lowest of the workweek.

-- The click rate starts to sag, too, at 4.1%, fourth-lowest of the workweek.

Thursday: Open but Not Clicked

-- 22.4% of commercial email goes out on Thursday, making it the third-busiest day of the week.

-- The open rate lifts slightly -- up to 32.3%, second-best behind Monday -- but the click rate sags to 2.8%, the lowest all week.

"Thursdays are still good days to send, though. You get a lower click rate for either newsletters or ads, but a higher read rate," Mills says.

Friday: Not Too Shabby

-- Email volume is the lowest of the workweek -- 7.4% -- but just under one-third of it gets opened, and the 4.4% click rate is the second-highest of the week after Monday.

-- Email doesn't get opened or clicked on much after noon. All but one of the top 10 peak hours for open rates occurs between midnight and noon. More Time of Day Observations:

-- Nine a.m. PT is the peak hour for sending, opening and clicking on email for every day in the week except Tuesday. -- Although people tend to open email in relatively narrow bands of time from mid-morning to late afternoon, clicks happen all day long.

This is especially on Tuesday, when the top 10 hourly click rates ranged from 1 a.m. to 11 p.m. PT. Friday.

-- As the week wears on, people wait until later and later in the day to deal with their email.

On Monday, open rates start to plummet after 1 p.m. PT, except for a brief lift in late evening. 6 p.m. is one of the peak opening times on Wednesday, and by Thursday, sizable opens were being recorded as late as 7 and 11 p.m. PT.

"You can assume that there's a lot of scanning of email and group-deleting, so even if they're opening the email, they aren't necessarily reading it," Buchanan says.

Okay, Let's Start Sending on Monday! (Not)

Whoa buddy, not so fast. The data might be showing you a new opportunity to boost your returns, but just shifting to Monday probably won't solve your problems.

After all, what if Tuesday or Wednesday really is the best day for you to send to your particular audience? Even a one-day shift could torpedo your efforts.

If you're not happy with what you're seeing, though, changing the day could help you as long as it makes sense for your readers and your organization.

Run this experiment first: Look at your open, click or conversion rates (or whatever metric you use to measure a campaign's success) and compare them with your delivery rate.

If your delivery rate has remained relatively stable, but you notice your other metrics are declining against it, then maybe changing the day you send could give you a lift.

Step #1: Test

Yeah, testing is boring and sometimes expensive. But you might discover a few things about your audience you didn't know.

"If you send to IT people, they might not have time to read your emails until 6 p.m. or so, so that might really be the best time to deliver for your audience, even if the statistics show 9 a.m. gets the best open or read rate," Mills says.

Test a campaign by delivering half on Monday and half on your usual day, and compare the results. It's not strictly scientific, but it could generate some telling results.

Step #2. Get Your Back End in Shape

First, a word about your delivery rate. Stability isn't everything. If you're not delivering 75% or better (whether it goes to the in-box or the bulk-mail folder), you have problems that you won't fix by changing your send day.

Clean your list, review your delivery logs for trouble spots, get advice from your email broadcaster, and then start measuring again. Publish for at least three cycles or campaigns before you make any radical changes.

Then, look at your entire email production system. Which departments would have to change their schedules or deadlines? Can your IT, marketing or creative staff accommodate a change quickly?

Also, ask your email broadcast vendor if a day change would affect operations on its end. Under normal circumstances, the day you send shouldn't affect your vendor's own operations, but if you send a million emails or more at a time, you could disrupt their own schedule.

Remember: You Can't Always Control Delivery Timing

Just because you schedule a mailing to go out at 9 a.m. doesn't mean it will arrive in your recipients' inboxes at 9 a.m., 9:30 or even 10 a.m.

Some broadcast email clients "throttle" delivery in order not to overwhelm ISPs or set off spam filters triggered by too many messages in too short a time. This is a classic problem with AOL.

Also, many broadcast services will try at least three times to deliver a message. If your mailing list generates lots of soft bounces (rejection for any reason other than an invalid address) on the first try, the system will try again an hour or two later, and then take a third pass five, six, up to 12 hours later.

The cleaner your list, the more likely you'll hit your targeted send time.

One other caution: The "Monday effect" could wear off once the word gets out and everybody starts to send on Monday. Maybe Tuesday will start looking good again.

Useful links related to this story:

PDF of charts and graphs from the study: http://www.marketingsherpa.com/eROI_Version2UPDATED.pdf

eROI: http://www.eroidelivers.com/