We’ve written a lot about how senders end up in the spam folder, and why Internet Service Providers (ISPs) place senders there. But what about recipients? What do they consider to be spam? And what influences them to mark your email as spam?

We talked to recipients across the U.S. and U.K. to find out how they engage and interact with email. While the majority of this research can be found in the 2019 Email Benchmark and Engagement Study, this article focuses on additional data relating to how recipients interact with spam.

How do recipients define spam?

Recipients consider spam as email that is unwanted and generally separate spam email into 2 categories.

The first category is email that is annoying. This type of spam is typically promotional and inundates the inbox with multiple emails each week or each day. The email can also be irrelevant to the recipient or too repetitive in its offerings. While annoying, this email is harmless. 

The second category is considered dangerous email. This spam contains scams, inappropriate content, malware, viruses, or phishing attempts. Opening this type of email and clicking a link or attachment could prove harmful to your computer and data.

How do recipients interact with spam email?

We found that recipients are more likely to delete annoying emails first, especially when they’re on mobile devices. It’s easier for them to swipe and clear the email than it is to unsubscribe or mark it as spam. In the quote below, the recipient explains how inconvenient it is to unsubscribe or mark a sender as spam.

“It’s just more hassle. Sometimes you have to log in and deselect things, and it takes too long…” UK, Gen Z 

If the email is a glaring example of spam, they’ll mark it as spam and let the filters prevent future appearances. 

Sender Tip: Make it as easy as possible for recipients to unsubscribe. The easier it is to unsubscribe, the less likely your recipients will mark your email as spam. 

A secondary account for spam

Another way recipients interact (or avoid interacting) with spam is by having a secondary email account. 38% of respondents reported that they have a secondary account for spam and other unwanted emails. 

Recipients don’t want their primary inbox flooded with spam and use the secondary address as a catch-all of unwanted email. As you might guess, this secondary inbox is checked much less frequently than the primary inbox.

Sender Tip: This is a good reminder for senders to frequently clean out their unengaged contacts. There’s no point in sending to unchecked inboxes.

How do recipients identify spam? 

Business Type

We found that recipients are more likely to consider certain types of businesses to send spam than others. These include dating sites, drugs or pharmaceuticals, quick loans, and get-rich schemes.

Sender Tip: If you’re in this business category, you have to be especially careful that the recipients you send to truly want your email. Set up a confirmation email that requires recipients to verify and confirm their email address before they are officially subscribed to your mailing list.

Sender Name

If recipients don’t recognize the sender name, they’re much more likely to flag an email as spam. 

Take a look at the sender name in this example. The sender is “newsletter.” This doesn’t tell you who is actually sending the email, but rather the type of email being sent. Not identifying the sender makes the recipient suspicious that the email is spam. 

Sender Tip: Choose an address and sender name that is recognizable, and avoid sending emails with “no reply” in the address. You can use your business’ name or the name of a well-known person at your company. 

This is especially important for transactional emails. Providing a recognizable name for your transactional emails builds trust and a sense of security with your recipients who are expecting to receive time-sensitive, important information from you. 

Subject line

There are a number of tell-tale signs in a subject line that let the recipient know this email could be spam. Recipients are particularly suspicious of subject lines that include:

  • All caps: Feels unprofessional and aggressive, as if someone is “yelling” in your inbox.
  • Emojis: Younger generations are more open to emojis in the subject line, but too many emojis (more than 2) look spammy to all generations.
  • Promises that are too good to be true: Messages like, “You’ll make millions,” or “Sign up today to win X,” feel suspicious and unrealistic to recipients. 

Take a look at the subject lines below that I found in my spam folder. In the first subject line, the multiple emojis are overkill while the message to find a boyfriend based on your zodiac feels far-fetched at best.

In the second subject line, the mixture of emojis, all caps, and the discount most likely contributed to this email landing in the spam folder.


Emails with images that don’t load, basic plain text emails, and emails that include attachments are all red flags for recipients, especially after hearing their colleagues’ horror stories of viruses taking over their computer after opening an unknown attachment.

Check out a few examples below of emails that were either immediately sent to spam by the ISP or flagged by the recipient as spam.

Examples of spam emails

In the two emails below, one of the biggest identifiers of spam is that none of the images load. It’s challenging to understand the purpose of the email without the images, and makes the recipient wary of clicking on any of the links.

The bright, jarring colors in this email and the unusual call-to-action (CTA) in the top right corner to “call now for unpublished deals” are both warning signs that this email is spam.

In this email, the number of emojis, plain text message, and the inappropriate content lead the recipient to believe this is not a safe sender.

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Recipients are savvy consumers of email, and can usually tell when something doesn’t look right in their inbox. 

When sending your emails, create an experience for your recipients that builds trust for your brand. You can do this by:

  • Using a familiar sender name
  • Staying aways from all caps and emojis in the subject line
  • Prioritizing email design so your images and links render correctly

To learn about spam from the sender’s side and how to prevent your emails from landing in the spam folder, download our guide, Top 10 Tips and Tricks for Staying Out of the Spam Folder.

Julie is the content marketing manager at Twilio SendGrid, helping to write and edit the blog, as well as enhance SendGrid’s SEO efforts. When she isn’t at the office, you’ll find her buzzing around Denver’s coffee shops, breweries, and yoga studios.