The complete email deliverability checklist.

Bad actors love to abuse sign-up forms by automatically submitting emails via bots. Implement a CAPTCHA such as Cloudflare Turnstile or use a WAF service like Cloudflare or Wafris to detect and block automated attempts before they reach your server.

Limit the number of form submissions per day per IP address to stop spammers from flooding your sign-up forms. Also consider a global rate limit to stop distributed attacks across multiple IPs.

Spammers often abuse authentication forms to create bulk accounts. Implement rate limits on sign-ups, invitations, and password resets per IP per day.

Don't allow personalization fields (first_name, last_name) in initial emails. These can be abused to inject malicious links or spam content.

If you deal with a high volume of sign-ups, consider using StopForumSpam.com to detect known bad IP addresses and emails.

Every form should clearly tell users what emails they will receive after submission. Only send emails that match what the user consented to.

Use a validation service to check email addresses at the point of entry. This catches misspellings and obvious spam addresses before they hit your list.

Many bots look for simple single-field forms. Making forms multi-step where the input is hidden behind an interaction reduces automated sign-ups significantly.

Honeypot fields are invisible to real users but get filled by bots, making it easy to detect and block automated submissions.

Block submissions that happen impossibly fast (under 1 second). Real humans take time to fill out forms.

Confirmed Opt-In requires users to verify their email before receiving further emails. It is the best way to ensure subscribers actually want your emails and is highly encouraged by blocklist providers like Spamhaus.

Once an email hits your platform, run MX record checks and advanced validation. Misspelled, malformed, or undeliverable addresses should be unsubscribed immediately.

Don't overwhelm new subscribers. Ask yourself whether the user actually wants each email you're about to send.

Your first email should set expectations about what the subscriber will receive, how to unsubscribe, and how to contact you.

Sending from healthy, reputable IP addresses matters. Choose a provider that actively monitors sender quality and works with you on issues.

DKIM records verify that your email providers are authorized to send email from your domain. Use aboutmy.email to verify your setup.

Configure your ReturnPath domain correctly so email providers can verify you authorized the sending server. Use aboutmy.email to verify.

DMARC ensures all emails from your domain are authenticated and prevents unauthorized servers from spoofing your domain.

Brand Indicators for Message Identification displays your logo in email clients. Requires a trademark registration first.

Your domain WHOIS records should be accurate, current, and public. Anonymous WHOIS is viewed negatively by blocklist providers.

Every email you send should have a real inbox for replies. Whether a custom Reply-to or a monitored inbox, make sure replies reach a human.

When migrating, import only clean lists. Ensure unsubscribed, bounced, and spam-marked addresses are handled correctly by the new provider.

Send slowly and in batches when starting on a new platform. This gives your new IP addresses time to build reputation.

Only email people who have explicitly opted in and expect your emails. Confirmed Opt-In is the gold standard here.

Segment your list by engagement and focus on users who actively interact with your emails and business.

Subject lines should accurately represent your email content. Avoid emojis, clickbait, or misleading phrases that trigger spam filters.

Keep email body content clear and easy to understand. Don't use manipulative language or excessive HTML.

Place an unsubscribe link in both the header and footer of every email. Easy unsubscription reduces spam reports.

Let users choose what types of emails they receive. Not every subscriber wants every type of email.

Provide a clear way for users to reach you, especially for reporting abuse. Quick response prevents escalation.

Physical address and contact details are legally required in many countries and build trust with recipients.

Remove inactive users and addresses that never open your emails. A clean list protects your sender reputation.

Link shorteners (bit.ly, etc.) are heavily used by spammers. Avoid them in emails entirely.

All links in your emails should use HTTPS. Insecure HTTP links erode trust and can trigger spam filters.

Reducing tracking can improve deliverability and user trust. Weigh the tradeoff against engagement data.

Build an automated process that contacts inactive users and removes them if they still do not engage. This keeps your list healthy over time.