[FAQ]

Hi there,

I’m working on improving my email marketing and I’ve read a lot about what makes a good subject line – like being clear, personal, and creating curiosity. But now I’m wondering about the other side of it.

What are the things I should absolutely AVOID putting in my email subject lines in 2025 to make sure I have good deliverability and don’t turn off my subscribers? I’m thinking about specific punctuation, types of phrasing, capitalization, or other common mistakes that are red flags.

Thanks for helping me avoid any common errors!

[Jeff Bullas]

To write effective email subject lines that build trust with your audience and maintain good deliverability, there are several common practices and elements that you should generally avoid.

First, and most importantly, avoid using deceptive or misleading information. A subject line that makes a promise that the email’s content does not deliver on is the definition of clickbait. While it might trick someone into opening the email once, it quickly erodes trust and can lead to a higher rate of unsubscribes and spam complaints, which will damage your long-term sender reputation.

Second, you should steer clear of writing in all capital letters. A subject line typed in all caps is generally perceived as shouting by the recipient and can look unprofessional. It is also a classic flag for spam filters.

Third, do not use excessive or unnecessary punctuation. This particularly applies to using multiple exclamation marks or question marks at the end of a subject line. This type of formatting can also appear spammy and unprofessional.

Fourth, while a single, relevant emoji can sometimes be effective depending on your brand and audience, avoid overusing them. A long string of emojis can make your subject line look like junk mail and may not display correctly across all email clients.

Fifth, be cautious with overly “salesy” or hype-filled language. Phrases that sound like a high-pressure sales pitch, such as “Once in a lifetime opportunity” or “Act now before it’s gone forever!”, can sometimes be flagged by spam filters and can be off-putting to subscribers, depending on the context and your relationship with them.

Sixth, always proofread for typos and grammatical errors. A subject line with a spelling mistake immediately makes your communication look careless and can undermine the credibility of your brand.

And seventh, do not use “Re:” or “Fwd:” prefixes deceptively. Adding these to a marketing email subject line to make it appear as though it is part of an ongoing personal conversation is a misleading tactic that will destroy trust once the recipient opens the email.

In essence, the goal of a subject line is to be a clear, honest, and compelling preview of the valuable content inside your email. Avoiding these common mistakes will help you maintain a professional image, build a stronger relationship with your subscribers, and improve your overall email deliverability.

Cheers,

Jeff

[Author]

Posts