Will using a dollar sign in an email subject line cause spam issues?
Michael Ko
Co-founder & CEO, Suped
Published 2 Jun 2025
Updated 15 Aug 2025
7 min read
A common concern among email marketers and senders is whether using special characters, like the dollar sign ($), in subject lines will automatically land their emails in the spam folder. It's a question rooted in years of evolving spam filter algorithms and the constant battle against unwanted messages.
The short answer is no, a dollar sign alone won't doom your email. However, the longer answer involves understanding how spam filters actually work and the context in which these symbols are used.
The myth of the instant dollar sign spam trigger
For a long time, there was a belief that even a single dollar sign could trigger spam filters, particularly older ones like SpamAssassin, due to rules designed to flag 'money-oriented' or overly commercial content. While such rules, like the LOTS_OF_MONEY rule, did exist, their impact was often minimal, and they often focused on the email body rather than just the subject line.
Modern spam filters are much more sophisticated. They analyze hundreds, if not thousands, of factors beyond just a single character. This includes sender reputation, engagement metrics, email authentication (SPF, DKIM, DMARC), content relevance, and recipient behavior. A lone dollar sign in a legitimate, opt-in email about a transaction or a specific discount is unlikely to be the sole reason for it going to spam.
If you're using a specific amount, such as "A chance to win $100 gift voucher for completing our survey", the amount itself, when used transparently and appropriately, is generally not an issue. The problem arises when such symbols are combined with other elements that indicate spammy behavior, which we'll explore further.
Context matters: when dollar signs can become an issue
While a single dollar sign isn't a red flag, its context is everything. Overusing any special character, including the dollar sign, or combining it with other spammy tactics can certainly increase your chances of being blocklisted (or blacklisted, if you prefer that term) or flagged by filters. For example, excessive use of symbols like "!!!", "$$$", or "100%" is often associated with deceptive or unwanted emails, as documented by SnapSurveys.
Spam filters (and recipients) are wary of subject lines that scream FREE MONEY or GUARANTEED INCOME. The key is whether the use of the dollar sign is part of a genuinely helpful or relevant message to a willing recipient, or if it contributes to a misleading or overly promotional tone. This ties into the broader issue of how email keywords trigger spam filters.
Consider the difference between a transactional email, like an invoice notification with "Your bill is $X.XX due soon," and a marketing email with "$$$ MAKE MONEY FAST $$$!" The former is expected and legitimate, while the latter aligns with typical spam patterns. Email providers prioritize user experience, so anything that looks deceptive or manipulative will be scrutinized.
Risky usage
Excessive symbols: Using multiple dollar signs (e.g., "$$$ BIG DISCOUNT $$$!") or combining them with other attention-grabbing characters like exclamation points or asterisks.
Deceptive offers: Subject lines promising unrealistic financial gains or using monetary symbols to mislead recipients about content, which can fall under CAN-SPAM Act violations.
Irrelevant context: Using dollar signs in emails where money or financial offers are not the primary, legitimate focus.
Beyond symbols: the real factors influencing deliverability
The true determinants of email deliverability extend far beyond the presence of a dollar sign. Factors like your sender reputation, email authentication, and recipient engagement play a much more critical role. A poor sender reputation, for instance, can lead to your emails being flagged as spam regardless of your subject line content.
Email authentication protocols such as SPF, DKIM, and DMARC are fundamental. If your emails aren't properly authenticated, they're much more likely to be seen as suspicious and diverted to the spam folder, even with a perfectly innocent subject line. You can learn more about these in our simple guide to DMARC, SPF, and DKIM.
Recipient engagement is also key. If your subscribers consistently open, click, and reply to your emails, it signals to inbox providers that your content is valued. Conversely, low open rates, high unsubscribe rates, and frequent spam complaints will negatively impact your sender reputation, leading to deliverability issues, irrespective of a dollar sign in your subject line. This is why it's vital to avoid common email deliverability issues.
Many email providers, including Outlook and Gmail, also have sophisticated algorithms that learn from user interactions. If users consistently mark emails with certain subject line patterns (or from certain senders) as spam, those patterns will be flagged more aggressively in the future. Cendyn CRM notes that overusage of dollar signs, like exclamation points, can cause red flags but this is always in combination with other problematic factors.
Best practices for crafting financial subject lines
When incorporating monetary values or symbols into your email subject lines, prioritize clarity, relevance, and authenticity. Focus on providing value and setting accurate expectations for the recipient.
Be transparent: Ensure your subject line accurately reflects the email content. Don't use a dollar sign to entice opens if the email isn't about a financial offer or transaction.
Avoid excessive use: While one dollar sign is fine, multiple instances or a combination with other spam trigger characters can make your subject line look suspicious.
Focus on value: Highlight the benefit to the recipient rather than just the monetary amount. For example, instead of "Save $50!", consider "Unlock $50 in savings on your next purchase."
Segment your audience: Send financial offers only to segments of your audience who have expressed interest in similar content, ensuring higher engagement and lower spam complaints.
Remember, the effectiveness of your email subject line isn't just about avoiding spam filters, it's about enticing opens from interested recipients. A subject line that clearly communicates value, even with a dollar sign, will always perform better than one that relies on sensationalism.
Key takeaways for inbox success
Using a dollar sign in an email subject line is not inherently problematic and won't, by itself, cause your emails to go to spam. Modern spam filters are too sophisticated to rely on such a simplistic trigger. The real challenge lies in the overall context of your email, your sender reputation, proper email authentication, and whether your message genuinely provides value to an engaged audience. Focus on building trust and adhering to best practices, and a dollar sign in your subject line will merely be a symbol, not a spam trap.
Views from the trenches
Best practices
Always prioritize sender reputation and strong email authentication (SPF, DKIM, DMARC) over individual subject line characters.
Ensure that any monetary offer in your subject line is relevant and accurately reflects the content of the email.
Maintain a healthy email list with engaged subscribers to boost overall deliverability and inbox placement.
Test your subject lines with a small segment of your audience to gauge performance before a full send.
Monitor your deliverability metrics regularly to identify any potential issues early.
Common pitfalls
Overusing dollar signs or combining them with other spammy symbols (e.g., !!!, ***).
Employing deceptive or misleading subject lines that promise unrealistic financial returns.
Sending unsolicited emails, regardless of subject line content, which is the primary driver of spam complaints.
Neglecting fundamental email deliverability practices while focusing on minor subject line tweaks.
Assuming a single character or word is the sole reason for spam filtering, ignoring broader reputation issues.
Expert tips
Modern spam filters assess the entire email context, including sender history and recipient engagement, not just isolated characters.
The impact of specific symbols like '$' is often less significant than overall email hygiene and sender trustworthiness.
A low score from a specific spam rule, like SpamAssassin's `LOTS_OF_MONEY` (if active), rarely triggers spam filters on its own.
Focus on delivering clear, value-driven messages to an opted-in audience for optimal inbox placement.
If emails are landing in spam, investigate core issues like authentication, sender reputation, and content relevance first.
Expert view
Expert from Email Geeks says that using a dollar sign in subject lines is a myth and will not quickly end up in the spam folder, provided recipients have explicitly asked for the email.
2020-10-30 - Email Geeks
Marketer view
Marketer from Email Geeks notes that while a `LOTS_OF_MONEY` rule exists in SpamAssassin, a small amount like $100 would likely not trigger it, and the rule primarily searches the body, not the subject.
Outlook and 
Gmail, also have sophisticated algorithms that learn from user interactions. If users consistently mark emails with certain subject line patterns (or from certain senders) as spam, those patterns will be flagged more aggressively in the future. Cendyn CRM notes that overusage of dollar signs, like exclamation points, can cause red flags but this is always in combination with other problematic factors.
