How to Write Emails That Reach the Inbox
Last updated: March 26, 2026
Even well-written emails can end up in spam if you are not careful about how they are worded. This guide covers the key factors that affect whether your emails land in the inbox or get filtered out, and how to fix them.
📩 What Affects Deliverability
Email providers like Gmail, Outlook, and Yahoo decide whether to deliver your email to the inbox or send it to spam.
Three main factors influence that decision:
Domain reputation — Your sending domain builds a reputation over time based on how recipients interact with your emails. High bounce rates, spam complaints, and low engagement all hurt your reputation. A poor domain reputation means even good emails get filtered.
Good news: Domain reputation is handled on our side, so you don’t need to worry about it. AiSDR sets up and manages dedicated sending domains and takes care of maintaining their reputation. This means your primary domain stays safe, and you don’t have to manage technical details.
🔗 What AiSDR does to ensure good deliverability
Links in your emails — Every link you include gets scanned. Shortened URLs (like bit.ly), too many links, or links to low-reputation domains raise red flags.
Avoid using links in your initial email. In follow-ups, keep links to a minimum and only include them when necessary. Links hurt deliverability.
Language patterns — Spam filters analyze the words and phrases in your emails. Certain terms, especially those related to money, urgency, and too-good-to-be-true offers, are strong spam signals. This is the factor you have the most direct control over, and it is what the rest of this article focuses on.
AiSDR sends plain text emails by default, which avoids the deliverability risk of HTML formatting, images, and tracked links.
⚠ Spam Trigger Words and Phrases
Spam filters flag specific words and phrases that are commonly associated with unwanted or deceptive emails. Below is a table of common trigger words, why they are problematic, and how to rephrase them.
For the full list of 90+ spam trigger words, see the complete Email Spam Trigger Words spreadsheet.
Spam Word/Phrase | Why It Triggers Filters | Better Alternative |
Free | One of the most heavily flagged words. Signals promotional or scam content. | No cost to get started, or complimentary |
Buy now / Act now | Creates artificial urgency, a hallmark of spam. | Let me know if you would like to explore this |
Limited time offer | Pressure tactics are a top spam signal. | We are running this through [date] |
Click here | Vague link text is associated with phishing. | See the full breakdown here (with a descriptive link) |
Guaranteed | Overpromising is a strong spam indicator. | Based on what we have seen with similar companies |
No obligation | Sounds like a sales pitch rather than a real conversation. | Happy to walk you through it — no strings attached |
Double your income / Earn $ | Financial promises are among the highest-risk triggers. | Here is how [Company] grew revenue by 30% |
Discount / 50% off | Discount language signals promotional bulk email. | We have flexible pricing for teams like yours |
Cash / Cash bonus | Direct money references are heavily filtered. | Focus on the business value instead of money |
Congratulations / You have been selected | Classic phishing and lottery scam language. | I came across your profile and thought this might be relevant |
Risk-free | Sounds too good to be true, triggers skepticism filters. | We can show you results with a small test before any commitment |
Dear friend | Generic greetings signal mass, impersonal outreach. | Use the recipient's first name |
Increase revenue | Overly salesy financial language. | Help your team close more deals |
Call now | Direct call-to-action pressure triggers filters. | Would it make sense to hop on a quick call? |
Exclusive deal | Promotional language that signals bulk marketing. | I wanted to share something relevant to your team |
📈 Subject Line Best Practices
Your subject line is the first thing spam filters evaluate and the first thing your recipient sees.
A good subject line sounds like something a real person would write to a colleague, not a marketing blast.
Keep it short and specific. Aim for 5 to 9 words. Long subject lines look like marketing emails.
Avoid ALL CAPS and excessive punctuation. Writing like HUGE OPPORTUNITY!!! screams spam. Write naturally.
Do not lead with the recipient name. Something like John, exclusive offer inside is an obvious template. Use the name naturally if at all.
Skip promotional language entirely. Words like free, offer, deal, and discount in subject lines are major red flags.
Write like a human. Before sending, ask yourself: Would I write this subject line to a coworker? If not, rewrite it.
Bad vs. Improved Subject Lines
Bad Subject Line | Why It Is a Problem | Improved Version |
LIMITED TIME: 50% Off Our Services! | All caps, urgency, discount language | Quick question about your outreach stack |
FREE Demo — Act Now! | Free, Act now, exclamation mark | Saw your team is scaling — thought this might help |
Congratulations! You Have Been Selected | Classic spam/phishing pattern | Came across [Company] — had an idea |
Make Money Fast With Our Platform | Financial promise, too-good-to-be-true | How [Similar Company] cut prospecting time in half |
Do Not Miss This Exclusive Opportunity | Urgency + exclusive + vague | Interesting approach to [specific challenge] |
John, Claim Your Special Discount | Name + claim + discount = triple flag | John — quick thought on [topic] |
✍🏻 Rewriting Spammy Sentences
It is not just individual words; it is how your whole message reads. Here is how to transform common spammy sentences into emails that sound like they came from a real person.
Before: I am reaching out because we have an exclusive, limited-time offer that could double your revenue.
After: I noticed [Company] is growing quickly — we have helped similar teams streamline their outreach. Would it make sense to chat?
Before: Act now to claim your free trial and start making money today!
After: We offer a trial if you would like to see how it works with your workflow. Happy to set it up.
Before: Congratulations! You have been selected for a risk-free, guaranteed opportunity.
After: I came across your profile on LinkedIn and thought our tool might be a good fit for what you are building.
Before: Buy now and get 50% off — this deal will not last!
After: We have flexible pricing for smaller teams. Want me to send over the details?
Before: Dear friend, I have an incredible investment opportunity for you.
After: Hi [First Name], I saw that [Company] recently [specific event]. Thought this might be relevant.
To apply these rules to your AiSDR campaigns, add them to your persona's custom instructions or forbidden phrases. → How to Adjust Your Messaging
📌 Quick Checklist Before You Send
Check your email against the full spam trigger words list before sending.
Read your subject line out loud. Does it sound like something you would send to a coworker?
Avoid links in your emails where possible - especially in the first message.
Use the recipient's name and reference something specific about them or their company
Avoid all caps, excessive exclamation marks, and multiple question marks (??)
The bottom line: write emails the way you would write to a colleague. Keep them short, specific, and conversational. If your email could pass as a normal business message, it is much more likely to land in the inbox.