8 Tips for Crafting a Spam-free E-mail Subject Line

Himani Sheth
7 min readOct 30, 2017

E-mailers have been a major source of promotion for any marketing campaigns. According to one report, e-mails are the third most influential source of information for B2B audiences.

Colleague recommendations and industry-specific thought leaders are the first two. 59% of B2B marketers say e-mail is their most effective channel in terms of revenue generation.

As it is for any other facet, e-mails marketing is just as effective in case of events. From sending out invitations to the overall event sales, e-mail is a great tool for event planners.

According to HubSpot, over 75% of marketers use e-mails to promote their event, while 47% of them send out e-mails invites for their events. Event professionals have multiple types of e-mails that are to be sent out in order to successfully promote their event and generate revenue as well as maximize audience engagement.

There are various types of e-mailers that planners send out to the attendees:

- Invitation

- Promotional

- Informative

- Updates

- Feedback

Crafting the perfect e-mail is imperative. It is crucial that the first point of contact through e-mails doesn’t go in vain. Hence, you must take every step necessary to avoid your e-mails from falling into the e-mailer death trap. What death-trap, you ask? The Spam Folder.

If your e-mailers are going directly to the Spam, there is a very high chance that your message would be deleted even before the other person has a look at it.

So, how do you avoid your mailers from going to trash? By taking necessary precautions in terms of content, your mailing account, mailing services, etc.

Talking about e-mail content, the most important part of an e-mail’s content that can make or break your mailing campaign is the subject line. It is the first thing that an attendee sees while browsing through those thousands of e-mails lying into their account.

Here’s a fact that proves how important a subject line is as a deciding factor :

“69% of recipients report an e-mail as spam based on the subject line alone.”

But more importantly, the subject line is a valid decider of whether or not your e-mails are sent to spam. In order to understand how this works, it is important to understand how the spam folder works.

E-mails service providers have their own tech in place to detect possible spam mails. There are certain aspects of e-mails, from the e-mails address to the content that triggers these spam detectors.

Your e-mails are scored based on the number of variables that could potentially activate the spam detectors. The higher the spam score, the higher the possibility of your mail landing into spam. Hence, the e-mails must be crafted in such a way that you dodge these triggers.

Concerning the subject line, there are a lot of variables of an e-mails subject line that trigger the spam filter. In order to avoid this, there are certain rules that you need to follow while crafting your perfect subject line:

1. Do not begin your subject lines with questions like “Do you like/want/have…?”

E-mails beginning with such active questions that elicit a particular response from the receivers trigger spam detectors quite easily. In particular, question such as “Do you want/wish/ want to have” gets you a higher spam score. It is always best to avoid framing such subject lines.

Find an alternative, more subtle way to present the solutions that your product can provide to the customers, the ways in which the product can fulfill their needs rather than direct questioning.

2. Mind that punctuation!

Never use more than 2 punctuation marks in your subject line. Multiple punctuation marks raise your spam score. Also, using exclamation mark (!) in the subject line is to be avoided at all costs especially when it is preceded by a question mark (?).

Hence using phrases like, “What’s the meaning of life? You’d never have guessed!” will send you straight to the folder of doom. Apart from the exclamation point, single apostrophe (‘) is another landmine for marketers that is to be avoided.

3. Never Use All Caps:

Apart from being rude, a sentence in all caps is surely going to trigger the spam-checkers. Some people try to highlight a phrase or a word that they wish their customers to notice using capitalized letters.

All caps adds on to your overall spam score. Thus, even with good intentions, it is best to avoid highlighting certain aspects of your subject line with all caps. Use catchy lines to grab attention instead.

4. Subject line should be consistent with your e-mails content:

It is one thing to puff up your subject lines a bit to gain your lead’s attention. Crafting deceptive subject lines is an entirely different and most probably illegal practice.

There are a lot of spam mails that begin with the subject line along the lines of “The best deal of your life!” with content usually containing a subscription form or a media content of some kind. E-mails with subject lines that are inconsistent with the content that it promises to provide are sent right to spam.

5. Subject lines beginning with “Re:” or “Fwd:”

Spam filters consider e-mails with subject lines like “Re: [Your Subject]” or “Fwd: [Your Subject]” as spam when the e-mails are being sent to an account for the first time. Some marketers use this technique to trick customers.

Such subject lines are considered deceptive and are major trigger for spam. Even if you are forwarding the same message to a number of people, make sure that each subject line is a standalone mail rather than a reply or a forward. Hence, it is always good to personalize.

6. Long Subject Lines are a strict no no.

Short and precise subject lines work best for an e-mails marketing campaign. It is very much a possibility that your e-mails will be sent to spam if your subject line is too long. Apart from that, it will also affect your open rate in turn damaging your campaign.

Hence, it is always best to tailor your subject lines, keeping them to the point. A subject line with 50 characters or less is advisable. Ideally, a subject line with approximately 20 characters works best.

7. Avoid using spam words in subject line.

These spam detectors have a set list of spam words that are considered to be triggers. Surprisingly, using simple words like ‘solution’ or ‘one’ can trigger the software. There are certain words and symbols that are bound to send your e-mails to spam.

These include “Completely free,” “$” sign and any percentage that’s more than 100 i.e. using phrases like “Earn up to $10 with a 101% guarantee” will 101% send your e-mails right to spam. To make it easier, you can refer to Hubspot’s exhaustive list of spam trigger words.

8. Avoid overloading the subject line with keywords:

Keywords are god’s gift to marketers. When used right, keywords can provide that extra edge to your content that makes sure that your content reaches a huge audience and more importantly, the right audience. Keywords in e-mails are a common practice.

It gives a gist to your customers about the subject matter of the campaign. However, overloading your subject line with only keywords does just the opposite of what is intended and could potentially land your e-mail in spam.

Pro-tip: Browse through your e-mail account’s spam folder and see the kind of subject lines that these mails have. It will help you create your list of ‘don’ts’ while crafting your own subject lines apart from the above given pointers.


Here are a few more essential pointers for framing the perfect e-mail campaign, apart from the subject line to help you dodge that spam folder:

1. E-mails beginning with ‘Dear [Something]’ send your e-mails straight to spam.

2. Prefer attaching links rather than direct media attachments or embedding forms. Provide CTAs instead.

3. Avoid rich media such as JavaScript and videos.

4. Avoid using multiple font colours. Use no more than three font colours in total. E-mails containing red fonts automatically increases hour spam score.

5. Maintain sufficient text to image ratio. Ideally, a 60:40 text to image ratio is advisable.

6. Keep it short. Keep your e-mails under 500 characters as much as possible.

7. Avoid coding errors in case of HTML e-mailers. Incompetent HTML coding is a major trigger for spam.

8. Add a clear ‘Unsubscribe’ button that should be active at least a month after the mailer is sent.

9. Filter out your mailing list to remove inactive subscribers.

10. Ask your subscribers to add you into their contact list after first contact.

11. Use a verified independent e-mail to send out mailers.

12. If you are using Microsoft Outlook, do not mark your campaigns as ‘Of High Importance.’ It automatically triggers the spam filter.

Pro-tip: There are various tools in the market that help you check your e-mail campaigns spam score. Most of these rank your e-mails out of 10 or provide you with a spam percentage. The higher the score, the higher the chance of your e-mail going to trash.

It is always advisable to create a test campaign before executing an important e-mail marketing campaign. AB testing before the actual campaign can help you ensure the effectiveness of the e-mails campaign and point out the changes that are to be made to ensure maximum ROI.

If you would like to add on to this list, be sure to connect with us on Facebook, Twitter, and LinkedIn.

Would you like to know how Hubilo can help you create exceptional events? Know more about it here or talk to us.



Himani Sheth

Himani Sheth is a Mass Communication major with a love for writing. A bibliophile, a movie buff and an avid traveler, say hello to her at @HimaniSheth .