Skip to main content
All CollectionsCampaignsEmail Campaigns
Email Subject Line Best Practices
Email Subject Line Best Practices

Learn ways to improve your subject line performance

Ira avatar
Written by Ira
Updated over a week ago

Subject line is the first thing your subscribers see in their inbox, which determines whether they will open your email or not. Focusing on your email subject lines will help you gain more customers to open your emails, avoid emails going to spam folders, and get your messages seen.

This article will show you how to write effective subject lines and how to check your subject line performance.


Before you begin

  • There's no character limit for Subject Line length, but inboxes will show only a shorted part as a preview. You can check the inbox preview right next to your campaign's subject line field.

    Below is a list of email clients and their default character count displayed.

Email client

Character Length displayed

Outlook 2010 preview

54 characters

Outlook 2010 compact

73 characters


66 characters


70 characters

60 characters

Yahoo Mail

46 characters

Android (480 x 320px) portrait

27 characters

Android (480 x 320px) landscape

46 characters

Android (800 x 480px) portrait

30 characters

Android (800 x 480px) landscape

62 characters

iPhone portrait

41 characters

iPhone landscape

64 characters

Windows Phone portrait

42 characters

Windows Phone landscape

61 characters

Subject lines in campaigns and automations

The subject line is the first field you'll need to fill out in the Settings of your email campaigns. Continue reading to learn how to come up with effective subject lines.

For automations, you'll be able to customize the subject line for each email block as part of a workflow. You need to click on the selected email block and then edit the Subject line on the right-hand sidebar.

Subject line Tips

Keep the Subject Line Short and Simple

Email subject lines should be short, simple, and easy to read. If you use long, complicated words, people won't read your subject line. At best, their eyes will gloss over complex words; at worst - your customers will mark your emails as spam. It is essential to make the subject line interesting and relevant. This will get more people to open your emails and make you look better as a sender.

Use simple words in your subject line, but only a few. Ideally, there should be at most 5-7 words in a sentence. It's essential for your customers to be able to quickly scan through their inbox and focus on subject lines that caught their attention. Writing a short subject line with only one or two words can sometimes be better. This makes it much more likely for your customers to read the subject line. If the subject line is good, they will actually open and read the email.

Here are some examples of great short subject lines:

  • "Your Expertise is requested!";

  • "Question for you";

  • "You're invited!";

  • "Holiday Special";

  • "Are you coming?";

  • "Still thinking about it?"

  • "Here's Why We [Something Remarkable]";

  • "Last call: [Name Of Product] closes in [#] hours";

  • "Fix Your [Problem] Now".

Use Personalization

Another way to get more people to open your emails is to use personalization in the subject lines. The simplest way is to add a person's name in the subject line, but don't limit yourself to this. Instead, use a powerful personalization tool that Omnisend offers, start by using the customer's name and continue up to location-based offers.

Personalization has proven to make people more likely to open emails. It may be even better when combined with automations like birthday deals and after-sale follow-up emails.

A great email marketing strategy is to use the information you already know about your customers, for example, order history, which you can check by creating segments from your Audience in Omnisend. It's easier to write personalized subject lines if you segment your customers and write emails specific to them.

To add personalization to your Subject line, click on the tag sign and choose what information needs to be inserted from the dropdown menu.

Read more about personalization in Omnisend here.

Here are some examples of personalized subject lines:

  • β€œ[Name], meet [your new product/feature]”;

  • "We'd love your feedback, [Name]";

  • "Only the best for you, [Name]";

  • "Proof That [Product] Works";

  • "[Name], this is so you, and it's 70% off!";

  • "Hey [Name], we picked these for you!";

  • "Try Out [Product] For Yourself";

  • "Proof That [Product] Works";

  • "Be stylish in [Location]".

Numbers & Lists

Our brains are naturally drawn to numbers, so including numbers in your subject line makes your subject line naturally intriguing. Numbers and lists are easier for our brains to process, creating curiosity and promising a quick and easy read.

Numbers and list email subject lines stand out for the same reasons that punctuation does - they are more visually appealing. It's also better to use numerals instead of spelling numbers under 10 out, as it makes the number more obvious and saves characters used.

Here are some examples of using numbers and lists in subject lines:

  • "25% off your favorites";

  • "Two for two";

  • "Top 10 products in [Company]";

  • "9 Facts about [Product]";

  • "25% off your favorites";

  • "Back By Demand 25% Off";

  • "Spend 60 Minutes or Less with [Product]";

  • "21 ideas how to use [Product]".


The use of question marks and exclamation marks can help you emphasize your subject line.

An exclamation mark instantly adds friendliness and excitement to a sentence. For example, the subject lines "Get your free discount code!" or "Get your next purchase for half price!" sound more exciting than a simple period.

A question, on the other hand, can make people more engaged. Subject lines phrased as questions prove to perform better than similar subject lines that were phrased as statements. When using questions in subject lines, try to ask a specific and relevant question and then provide a straightforward answer in the email body.

It is also best to use no more than two or three punctuation marks in each subject line. Your email can look like spam if you use too many punctuation marks. This is especially true if you use a lot of special characters. Special characters are known to trigger SPAM filters occasionally, so you need to be mindful when using them.

Simple language, a question, and proper punctuation get people to open the email and read it. Punctuation is a huge part of a healthy email marketing strategy, so don't be afraid to mix up the punctuation you use in your subject lines.

Here are some examples of using punctuation in subject lines:

  • "[Product] Restocked and Price Drop!";

  • "New colors in old favorites!";

  • "Are you ready for the sale?";

  • "Shhh! Don't tell anyone about this discount!";

  • "You don't want FOMO, do you?";

  • "Hey, forgot something? Here's 20% off.";

  • "Quick favor?";

  • "[Name], do you remember us?".

Include a Call to Action and Urgency

Some people respond best to straightforward directions. If your email has a direct call to action, such as urging recipients to purchase your product, don't hesitate to make that clear in the subject line. It's good to make it clear to readers their next step. Otherwise, their eyes will just skim over your subject line, and they won't know they need to do something.

A good strategy is to communicate a sense of urgency and timeliness. The less time that recipients have to act, the more likely they will do so.

Here are some examples of creating urgency and using CTA:

  • "Last call: [Name Of Product] closes in [#] hours";

  • "Talk to Us";

  • "Give [Product] a Try";

  • "Be Awesome with [Product]";

  • "Save 20% with [Company]";

  • "Act fast and save 20% on [Product]";

  • "Hurry! Your discount is about to expire";

  • "Don't miss this deal";

  • "See what's on sale instantly";

  • "Claim your coupon now!";

  • "Reveal your offer today";

  • "Start saving on [Product type] today".

Avoid Spammy Subject Lines

Specific subject lines can really throw people off, but they can also cause your emails to be flagged as spam, which in the long run can hurt your sender's reputation and make your emails go directly to the spam folder. Below you can find some tips on what to avoid, not to make your subject lines spammy.

  1. Don't use CAPS in your subject lines. Using caps in an email can be effective only if you use it for a single word in a subject line, but it needs to be the right word. Fully capitalized subject lines look spammy and will be ignored by readers. Instead, use simple and engaging language to capture your reader's attention.

  2. Don't overuse punctuation. We advise using no more than two or three punctuation marks in each subject line. Your subject line is character-restricted, and exclamation marks might appear spammy. Special characters like *%&# also have been known to trigger spam filters, so use them carefully.

  3. Don't use spam words. Including certain trigger words in your subject line can activate a spam filter, even if it is a legitimate message. Avoid terms, phrases, and symbols like "$$$," "100% free," "cash off," "cheap," "weight loss," "serious cash, etc. Even if your email gets delivered, it may appear spammy to your subscribers.

  4. Don't send inconsistent content. The subject line should always be consistent with the content of your email. Writing misleading subject lines is illegal behavior that will undoubtedly trigger a spam filter.

  5. Don't begin your subject line with "Re:" or "Fwd." When sending an email to an account for the first time, subject lines like "Re: [Your Subject]" or "Fwd: [Your Subject]" are considered spam. Deceptive subject lines are a primary spam cause. Even if you're sending the identical message to many recipients, ensure sure each subject line is distinct from the others.

  6. Don't use long subject lines. Email marketing subject lines should be short and accurate. If your subject line is too lengthy, it may be sent to spam automatically.

    Learn what content to create for better deliverability here.

Subject line tester

To help you come up with your perfect subject line, we have created a subject line tester that verifies if your subject line matches our best practices.

Once you type in your subject line in the field, our tester will show you a detailed analysis with tips on improving length, wording, and scannability and will show you an inbox preview.

A/B test subject lines

A/B testing of subject lines compares how version A of subject line performs compared to version B of subject line within an audience, like a segment.

To start setting up your A/B Subject line (also, you can A/B test the sender's name and content along with the subject line), click on New Campaign under the Campaigns tab, locate the Email A/B test and click Create A/B test.

Once you create it, you'll be brought to the setup wizard. There you will be able to change all settings for your A/B campaign. Read a detailed guide about A/B testing content here.

Further resources

If you want to learn more about subject lines and different strategies, we suggest looking at our blog posts:

Did this answer your question?