Improve Email Deliverability

When sending emails, it’s important to understand that every message has a “sending score”—a measure of how likely your email is to reach the recipient’s inbox rather than being caught in a spam filter.

That score is affected by the content of your message, links, attachments, subject line, and even email signatures. The higher the score, the more likely your email is to be flagged as spam, delayed, or rejected entirely.

The good news? Most deliverability issues can be fixed quickly and easily. Here are the five most common causes—and how to resolve them.

1. Hyperlinks:

Links can greatly influence your sending score, especially if they aren’t secure or look suspicious.

• Always use https instead of http.
• Avoid link-shortening services like Bit.ly or TinyURL, which are frequently abused by spammers.
• Be mindful of long reply chains—each reply often duplicates links, multiplying your spam risk.

Pro Tip: Keep the number of links to a minimum, and make sure all of them point to reputable, secure sources.

2. Complex or Image-Heavy Email Signatures

Your email signature should look professional—but not overloaded. Too many links, images, or tracking pixels (the tiny invisible images that monitor opens) can push your message into the spam folder.

Even the signatures of people in a long email thread can impact your deliverability, not just your own.

Pro Tip: Keep signatures simple—just your name, title, company, and one or two secure links if necessary. Skip the tracking pixels and extra logos.

3. CC’ing Yourself

It might seem harmless to CC yourself on outgoing emails, but doing this repeatedly can signal to spam filters that the email is automated or suspicious.

Unless absolutely necessary, avoid CC’ing your own address—especially when replying to group messages or forwarding existing threads.

4. Spammy Phrases or Subject Lines

Spam filters are trained to flag certain words, symbols, or formatting patterns commonly used in scams or marketing blasts.

Avoid:

• ALL CAPS
• Excessive punctuation (!!!, ???)
• Emojis or symbols in subject lines
• Overly promotional terms like “Act Now,” “Limited Offer,” “Last Chance,” etc.

Pro Tip: Keep your language natural and your subject lines clear. If you’re not sure, review a trusted resource like Mailmeteor’s Spam Word Guide or ActiveCampaign’s Spam Word List.

5. Suspicious Files/Attachments

Attachments and file names can also trigger spam filters.

Sketchy attachments or random file names (like “q0949adkjgkjj5809sgjk.jpg”) or strange punctuation look suspicious to mail servers.

Pro Tip: Name files clearly and professionally (e.g., Invoice_1234_CustomerName.pdf). Write subject lines that describe the content accurately, without unnecessary flair or capitalization.

Bottom Line

Email deliverability problems are rarely caused by one thing alone—it’s usually a combination of small factors that push a message over the spam threshold. By tightening up your links, simplifying your signature, keeping language clean, and using secure attachments, you can drastically improve your chances of landing in the inbox every time.