This document analyzes data from 85,637 email campaigns totaling 1.7 billion emails sent and 232 million emails opened to determine what factors influence open rates. Some of the key findings include that shorter subject lines under 30 characters performed best, personalization like adding a name did not reliably increase opens, and polite language like "please" and "thanks" as well as asking questions increased opens while all-caps and exclamation points decreased opens. The document advocates testing assumptions and focusing on compelling subject lines written in a natural voice to increase email open rates.

1. WHY DO PEOPLE
OPEN EMAILS?
A look at 85,637 subject lines,
1.7b sends & 232m opens

2. EVERYONE GETS TOO MANY EMAILS

3. AND THE TRUTH IS, MOST
EMAILS AREN’T OPENED :(
The 85,637 email campaigns we looked at
totaled 1.7 billion sends. Only 232 million - or
13.53% - were opened.

4. BUT SOME EMAILS DID MUCH
BETTER THAN OTHERS
While 2 in 5 emails had open rates under
10%, 1 in 5 had an open rate above 50%.

5. WHY?
What is it that gets a person to
open an email?

6. AND HOW CAN SUBJECT LINES
INCREASE OR DECREASE OPEN RATES?

7. Using Mixpanel’s data, we put best pracMces
and convenMonal wisdom to the test.

8. HOW LONG SHOULD A
SUBJECT LINE BE?
40 to 60 characters?
30 to 50 characters?

9. NOPE
Under 30 characters works best.
(Literally, the shorter, the beRer.)

10. OPEN RATE BY SUBJECT LENGTH

11. WHY?
Why do open rates drop aTer
30 characters?

12. APPS LIKE GOOGLE’S INBOX TRUNCATE AFTER 30 CHARACTERS
MOBILE

13. PEOPLE READ EMAILS ON THEIR PHONES
It can be hard to get subject lines that short, but look at
the first 27 characters of your subject line and make
sure they’re compelling.
“Hunter Walk grew YouTube by…”

14. DOES PERSONALIZING AN
EMAIL INCREASE OPENS?

15. IT’S CERTAINLY POPULAR
1 in 14 subject lines use personalizaMon.
The most popular use case was inserMng the
recipients first name in the subject line.

16. BUT OVERALL, IT DECREASED
OPEN RATES :(
Personalized emails were only opened 9.34%
of the Mme (-3.29%)

17. PERSONALIZATION CAN BE
COMPELLING THOUGH
PersonalizaMon is a tool, and we don’t always use it well.
Just pung a name in a subject line won’t increase opens.
Other variables, like including the name of an item leT in
the cart, resulted in high open rates (34%).

18. HOW DOES WORD AND
PUNCTUATION CHOICE AFFECT
OPEN RATE?

19. BE NICE
Subject lines that use polite words like
“please”, “thanks”, and “sorry” have a
22.98% open rate (+9.45%).

20. AND DON’T SHOUT
Including a “!” dropped open rates down
to 10.92%. And emails with mulMple
exclamaMon marks were even lower.

21. ASK QUESTIONS
Emails that asked quesMons had a
15.21% open rate (+1.68%).

22. AND ANSWER THEM
Subject lines with “How to” were
opened 20.66% of the Mme (+7.13%).

23. USE INFORMAL LANGUAGE
Again and again, subject lines with
informal language had higher open
rates than their formal counterparts.

24. SAY THANKS, NOT THANK YOU

25. HELP BEATS ASSIST

26. CHECK, NOT VERIFY

27. GET DOUBLES RECEIVE

28. URGENCY DOESN’T
INCREASE OPENS
Words like “today”, “tomorrow”, “tonight”, or
“now” didn’t increase opens. In fact, they had a
slightly lower open rate, at 12.67%(-0.86%).

29. SALES-Y LANGUAGE DROPS
OPEN RATES
Emails with words like ‘offer’, ‘code’, ‘coupon’, ‘sale’,
‘$’, ‘discount’ have a 10.34% open rate (-3.19%).

30. “FREE” WORKS?
Yep. It’s got a 17.27% open rate. Why? Your guess
is as good as mine. But it’s working – so let’s all go
ruin it again.

31. DON’T BUILD TOMORROW’S EMAILS
WITH YESTERDAY’S BEST PRACTICES
Don’t write best pracMces in stone, be empatheMc
and think about your reader as a person. Talk like a
real person, be nice and be compelling.

32. justin.megahan@mixpanel.com
Read the full report at The Signal & email me your questions

33. WHY DO PEOPLE
OPEN EMAILS?
A look at 85,637 subject lines,
1.7b sends & 232m opens
CLICK TO TWEET