Best Subject Line For Cold Emails In 2025

Stop using “Quick question”.

Instead, use a subject line that doesn’t make you look like a salesperson.

In this article, I’ll cover the following:

- What you need to understand before writing your subject line
- Best subject line for cold emails
- Common mistakes when writing a subject line
- Final thoughts

What you need to understand before writing your subject line

If you use a subject line that makes you look like a salesperson, then no one will respond to your cold emails.

Subject lines like "Quick question" have been overused for years, and are ignored by almost all prospects.

I don’t know what’s worse, using “Quick question” as your subject line, or starting your email with “I hope this email finds you well”.

Your subject line needs to be something related to your prospect, which makes them think that you are specifically reaching out to them, and not to thousands of other people.

In the next section of this article, I’ll give some examples of what this can look like.

Best subject line for cold emails

As mentioned above, it’s extremely important that your subject line makes your prospect think that you are reaching out to them specifically, and not to thousands of other people.

People only respond to cold emails if they believe that it was written just for them; no one wants to respond to an automated email campaign.

Your subject line needs to be something that is specific to your prospects.

Example 1:

In the below cold email, I wrote “Instantly review on G2” as my subject line, since I made a list of people that gave our competitor (Instantly) a review on G2.

When someone receives this email, they think the email is just for them, because it’s extremely specific. I’m mentioning the review they gave to Instantly, that’s too specific for them to think my email is automated.

Additionally, I like to also tie the P.s. line at the bottom of my email to the subject line, so I’ll say something like: “Your review on Instantly’s G2 page caught my eye, prompting me to contact you”.

The combination of my subject line and P.s. line highlighting where I found the prospect makes it seem like I’m sending this email just to them, thus increasing my response rate.

Example 2:

If I was sending cold emails to manufacturing facilities in the US for solar installation, I could use the address of each facility in my subject and P.s. lines.

This would make my email seem very specific to each prospect, thus increasing the likelihood of them responding.

For example, my subject line might say something like: “{street_address} facility”

And my P.s. line might say something like:

“P.s. your facility at {street_address} is eligible for the REAP program, which is why I’m reaching out.”

Common mistakes when writing a subject line

Below are some common mistakes that people make when writing their subject lines:

• Capitalizing all letters or using exclamation marks (this will cause your emails to go to spam).

• Including spam trigger words.

• Using html elements like emojis (plain text has better deliverability).

• Using subject lines like “Quick question” which makes people ignore your emails as they immediately associate you with spam.

• Writing a subject line that has more than four words.

• Sounding promotional (you should sound like a colleague sending an email to another colleague).

• Writing a subject line that isn’t relevant to the content of your email. Your subject line must be related to the content in your email’s body, otherwise you aren’t CAN-SPAM compliant.

Final thoughts

You need to make your subject line relevant to your prospect.

I usually mention where I found them, something that they are currently doing/using, or something about their business that is related to my offer.

Do NOT use generic subject lines like “Quick question”, as prospects and ESPs associated these with spam.

If you want to learn more about how to write the perfect cold email, then check out my article How To Write A Cold Email.

I also recommend that you check out my article 4 Best Cold Email Templates In 2024 (30%+ Response Rate).