Saleswhale has sent over 3 million B2B/B2C emails for our customers. We've anonymized and analyzed millions of emails in our database to find key insights.

We compiled our top 5 hacks for writing magnetic email subject lines. Here's what we've learned over the years:

Our analysis of sent emails shows that the sweet spot for email subject length is 31-53 characters (5-9 words).

Anything greater than that decreases response rates by 31.8%. Emails that didn't receive a response had 12.7% more characters in the subject line than emails that did receive a response.

Be clear and concise. State the problem or call-to-action upfront. Remember – the subject line is meant to be a hook, not a full explanation.

Dale Carnegie, the pioneer of self-improvement writing, once said, “A person’s name is to that person, the sweetest, most important sound in any language.”

Including the recipient's first name displays your effort in personalizing the email. This small improvement is so powerful that it can increase your chance of receiving a reply by 69.2%.

You can do this on Saleswhale's Topics page by adding the lead's name as a {{merge tag}} in the subject line.

If someone you know referred you to the recipient, mention your referral explicitly in the subject line.

Don't wait to mention your referral in the opening sentence of your email. Your reader might not even open the email to find out. SalesLoft found that subject lines including the word "referred" enjoy a 536% higher response rate compared to the typical email.

Segment your referred leads into Saleswhale's Warm Referral Introduction template to quickly apply this hack.

Stop using numbers in your subject line. People associate numbers in the email subject with overly-salesy email content.

SalesLoft found that simply avoiding numbers in subject lines prevented a 32% decrease in reply rates. Make a soft-sell to avoid pushing away prospective customers before they even open your email.

While we've given you formulas to consider, you should always be experimenting with subject lines. Your audience is fickle, and trends change quickly.

Deviate from subject line norms to rise above the noise and grab your reader's attention. You don’t want to sound like an automated marketing email. Some examples include:

Getting leads to open your email is half the battle. Use these tips to write subject lines that command attention.