Most agree that with so many people reading their emails on their phones, more consumers now see emails soon after they are received no matter where they are or what else they are doing.
These people are also less likely to click through at this time, because they’re making the time-killing inbox check, performing an initial triage when they are checking email on the go. They may not want to wait for a Facebook feed or a webpage page to load that may or may not be mobile-optimised on an ambiguous signal strength. They may mark something requiring a click-through to read later when they have time and are on a reliable signal, e.g., at work on their desktop, or at home on their WiFi in front of the telly.
Some email clients even supply extra methods to triage the inbox. For example, Mailbox by Dropbox has a snooze option where you can tell the inbox to remove the email from the inbox and return to the top at a specified time. There are a few inbox apps that have features like this -- more for IOS than for Android, it seems.
This suggests that open rate is not the best metric to use to decide the best time to send emails, because so many people can check and open emails at one time, and will then decide if they want to click through later.
This leaves the option to try and send at the best time for customers to click through. This is often much later in the day for consumers -- but is it consistent day by day? (No). And if you send late, will you miss the masses of people who will engage bit by bit as the day goes on?
Could this result in inbox flooding at peak conversion time?
As usual, the advice is to test, test, test -- but now you can bear this new mobile context in mind.
As an email marketer, what are your goals?
Are you looking for conversions and purchases?
Then you should base your send-time tests on your current prime conversion times, which would be different on different days. Keep an eye on which devices customers purchase, compared to devices used just to open emails. You may find desktop use results in purchasing unless you have an app. Also if you accept PayPal, you stand a better chance of faster conversion via your mobile-optimised site, than if you ask for card details.
Are you brand-building and looking for opens, site traffic and social
This is far more likely to be dominated by mobile devices, since sharing to Facebook and Twitter is made easy by each mobile OS, as people like to spread the word and start discussions on their second screen.
Hopefully you are doing both, with different types of campaign to segments of your lists based on their activity or lack thereof.
I personally will read my pre-triaged emails in the evening before any new emails, unless a new one is from a brand I already know is very relevant and the subject line suggests even more. Any new emails that are a “maybe” will get triaged at some point, and some already triaged emails could be de-prioritised as I reassess their relevance at the time.