Nine subject line insider tips to get 50%+ open rates

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When doing cold outreach as a b2b company, one of the most impactful metrics is open rate. 47% of recipients open an email based on the subject line alone (invespcro), so by optimizing it you’ll maximize your opens.

A lot of businesses are writing less than ideal subject lines due to common mistakes and lack of understanding of cold emailing tactics, so today I am sharing with you nine subject line insider tips that have helped us and our customers get open rates between 40% and 70% so that you can apply them to your campaigns as well.

Before we jump into the details, here’s the list of the tips for quick reference:

1. use appropriate length for subject lines

2. don’t use tricks or clickbait subject lines for higher opens

3. avoid spam words

4. use relevant numbers and symbols

5. A/B test different subject lines

6. subject line should be a preview of your message

7. include personalization beyond static placeholders

8. spell-check your subject line before sending

9. avoid requesting favors in the subject line

Note: all sources of statistics mentioned are listed at the bottom of the page.

1. use appropriate length for subject lines

To choose the right length for the subject line, you have to know the number of characters shown in the recipient’s screen. Desktops and tablets (landscape orientation) display between 40-70 characters of the subject line and smartphone screens show 30-60, so I recommend keeping the number of characters around 60.

Furthermore, when a prospect receives your email, the first few words of the email message are also displayed in the inbox preview snippet. In larger screens (desktop and tablets) the length of your subject line will impact the number of first few words from the email message that appear because they are in the same line, as shown below:

On smaller screens, however, the subject line and first few words of the email are shown in two rows, so you don’t have to worry about the impact of the length of your subject line, like in this photo:

Either way, the start of the email is visible so you have to take the words into consideration because they can impact the reaction of the recipient.

Good subject line:
{{companyId.shortName}} + hubsell – how about we team up

2. don’t use tricks or clickbait subject lines for higher opens

“69% of email recipients report email as spam based solely on the subject line.” – invespcro

A big mistake a lot of salespeople make is to write dramatic or over-promising subject lines that convince the target to open an email that doesn’t deliver on what was promised. That will not only annoy them but also disappoint them. They will remember you and your company in a negative light.

So using tricks or clickbait not only fails to deliver the desired result (which is to get a non-negative reply) but causes damage to your image and that of your brand’s.

A common example of a clickbait strategy is to include ‘fwd:’ in your subject line to pretend that the recipient knows you.

I would recommend against this because, according to invespcro, emails with ‘fwd:’ were opened 17% less than those without. Even if they open the email it will likely end up in the trash because they will feel tricked.

Bad subject lines:
Grow your lead generation by 2000% with outbound sales in 2 weeks
fwd: Grow your lead generation with outbound sales

3. avoid spam words

“Subject lines that use the word ‘free’ have significantly lower engagement rates (13.1% versus 17.2% for lines without ‘free’).” – sendgrid

Do not use spam words such as ‘free’, ‘money’, ‘risk free’, ‘apply now’, ‘credit’ etc (the list is huge and often times contextual). There are two cases against using spam words, 1) they are monitored by servers and will increase the chance that your email lands in the spam folder hence the name ‘spam words’, 2) they’re considered clickbait, unprofessional and disingenuous.

Bad subject line:
Grow your lead generation with outbound sales risk-free

4. use relevant numbers and symbols

In general, some numbers and symbols can be used in subject lines with success, but keep the following in mind to do it right:

Symbols like // and – and () can be used to separate and clarify the subject, but others like * ~ ^ % $ # should not be used because they are generally associated with spam emails.

A question can be a very useful tool in a subject line because it provokes the curiosity of the recipient, however, by using more than one you eliminate its effect and it can even hurt your conversions.

Attention seeking strategies like using CAPS or exclamation marks are not recommended for cold outreach because they can seem unprofessional.

Some of our customers have tried different strategies like ending their subject lines with an ellipsis, and it has worked for them, so feel free to experiment.

Regarding numbers, they should be relevant to the message, and any number below 10 should be spelled in ordinal form (ex: one; not 1).

Bad subject line:
Grow your lead generation at 40% off
{{companyId.shortName}} + hubsell – how about we team up??
ATTENTION: Grow your lead generation with outbound sales
Grow your lead generation with outbound sales!!

5. A/B test different subject lines

If you’re just starting your cold email outreach and are in the lower end of daily emails sent, then A/B testing might not be necessary yet, however, at some point, you’ll want to start trying out different subject lines to see if you can optimize your results.

The important thing to keep in mind is to never change too many variables at once in the subject or else you won’t be able to track what actually made a difference. A simple recommendation is to switch one aspect at a time and run the campaign long enough to analyze the effects.

Also, there is a fine line between good subject lines and spammy ones, but sometimes it is not a bad idea to test those boundaries, so try to come up with ideas that differentiate you from the competition.

Example of A/B testing:
{{companyId.shortName}} + hubsell – how about we team up
Increase ROI through outbound techniques with hubsell

6. subject line should be a preview of your message

“Don’t get too creative. The best email subject lines describe what’s in the email, without a hard sell.” – mailchimp

Make sure your subject line briefly summarizes the email to show the recipient you respect their time and that you are being sincere in your approach. This will lead to higher engagement and positive replies.

Furthermore, to persuade the prospect to open the email the subject has to be relevant to them. One example is to focus on a problem they have and how you’re going to fix it.

Good subject line:
{{companyId.shortName}} + hubsell – business leads and sales opportunities

7. include personalisation beyond static placeholders

“Personalized subject lines are 22.2% more likely to be opened.” – invespcro

Personalization is key to attain better conversion in your campaigns, and a simple way to do it is include the name of the prospect in the subject, which according to Hubspot, will result in higher open rates.

The next level of personalization is using dynamic placeholders that enable 100% customization of your subject lines to get even better conversions. We introduced this feature in our software due to demand from our customers.

Example of dynamic placeholders:
(If prospect is in business development) {{companyId.shortName}} + hubsell – business trends and developments
(If prospect is in sales) {{companyId.shortName}} + hubsell – business leads and sales opportunities

8. spell-check your subject line before sending

As the CEO of hubsell, I receive a lot of unsolicited emails from salespeople, so I’ve seen the good, the bad and the ugly regarding subject lines.

A common occurrence is subject lines that have some form of grammatical or spelling mistake in them. This usually leads me to think one of two ways 1) the sender is not prepared for the first impression with a prospect, so they will likely not be a good business partnership, 2) the sender does not have a high level of the language you’re writing in, which might result in misunderstandings in the future due to language barriers.

Either one of the scenarios mentioned above do not help you in any way, so make sure you check your subject lines and emails thoroughly before starting your campaigns.

Bad subject lines:
2019 – tell your brand stroy now!
Grow you’re lead generation with hubsell

9. avoid requesting favors in the subject line

Requesting favors or actions from prospects should only happen when there is some rapport. If the prospect has never met you before, there won’t be any connection between you two when they read your subject line. Therefore, I recommended that you avoid sentences like ‘requesting a quick call’ or ‘quick request’.

Another reason for why requests don’t perform well in the subject is because most decision makers are busy people that don’t have time to attend to them, so they will most likely compartmentalize you into the spam section.

Bad subject lines:
Quick call with our solution Experts.
Technology Partnership – Request a Call


In this article, I broke down the top tips to help salespeople boost open rates by improving their subject lines, in order to deliver more prospects to account managers. Here are the main takeaways from this post:

1. keep subject lines at around 60 characters and consider the first words of your actual email because they appear in the main inbox

2 .tricking or click baiting the recipient will lower your open and positive reply rates

3. avoid spam words like “guarantee”, “free”, “money” or “credit”

4. relevant numbers and non-disruptive symbols (ex: // and () ) can be used, and one question mark is useful but two become spammy; also, avoid CAPS and exclamation marks

5. A/B testing is the name of the game to reach 50%+ open rates

6. subject lines should be clear and summarize the message

7. personalize your subject lines with names and dynamic placeholders to increase conversions

8. spell-check your subject lines to avoid looking unprofessional

9. don’t request anything before having rapport with the recipient

Finding the ideal subject lines for your campaigns is all about testing because every company is in a unique situation due to having different products and target markets. However, by implementing the tips we have provided in this article, hopefully, you’ll be able to increase your email open rates.

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