How I Would Fix emails landing in spam in a Lovable plus Supabase paid acquisition funnel Using Launch Ready.

How I Would Fix emails landing in spam in a Lovable plus Supabase paid acquisition funnel Using Launch Ready

If your paid acquisition funnel is sending emails to spam, I treat it as a revenue leak, not a minor deliverability issue. The most likely cause is weak or missing domain authentication, usually SPF, DKIM, and DMARC not being aligned with the actual sender.

The first thing I would inspect is the sending domain setup end to end: DNS records, the actual email service used by Supabase or your SMTP provider, and whether the "From" address matches the authenticated domain. In a funnel, one bad email can kill trial starts, booked calls, and checkout completion.

Triage in the First Hour

I would start with the fastest checks that tell me whether this is a DNS problem, a sender reputation problem, or an app configuration problem.

1. Check the exact email source.

• Confirm whether Lovable is triggering Supabase auth emails, transactional emails, or custom SMTP.
• Identify the real sending provider: Supabase default email service, Resend, Postmark, SendGrid, Mailgun, or another SMTP relay.

2. Inspect DNS records for the sending domain.

• Verify SPF exists and has only one record.
• Verify DKIM is published and matches the provider.
• Verify DMARC exists and points to an inbox you control for reports.

3. Open Supabase Auth settings.

• Check SMTP configuration.
• Confirm sender name, sender address, reply-to address, and site URL.
• Confirm there are no stale test credentials or old project references.

4. Review recent deployments from Lovable.

• Check whether the funnel was deployed with a changed domain, preview URL, or environment variable mismatch.
• Look for hardcoded links pointing to staging instead of production.

5. Test the message headers.

• Send a test email to Gmail and Outlook.
• Inspect headers for SPF pass/fail, DKIM pass/fail, DMARC alignment, and any suspicious routing.

6. Check reputation signals.

• Look at bounce rate, complaint rate, and open rate if your provider exposes them.
• If you see sudden drops after launch or traffic spikes from ads, assume reputation damage until proven otherwise.

7. Review Cloudflare and SSL status.

• Make sure the main funnel domain resolves correctly over HTTPS.
• Confirm redirects are clean and there are no mixed-domain hops that can confuse trust signals.

8. Inspect logs for auth-triggered failures.

• Look for repeated resend loops from signups or password resets.
• Check for bot traffic causing high-volume email sends.

A simple diagnosis flow looks like this:

Root Causes

Here are the causes I see most often in Lovable plus Supabase funnels.

| Likely cause | What it looks like | How I confirm it | |---|---|---| | Missing SPF | Gmail accepts mail but marks it suspicious | DNS lookup shows no SPF record or multiple SPF records | | Missing DKIM | Email body looks fine but fails authentication | Message headers show DKIM fail or no signature | | DMARC not aligned | SPF/DKIM may pass but still land in spam | Header shows alignment fail between From domain and authenticated domain | | Wrong sender domain | Emails sent from a generic subdomain or provider domain | Supabase SMTP settings show an unbranded From address | | Bad list quality or bot signups | High bounce rate after ad traffic starts | Provider dashboard shows bounces from fake addresses | | Staging links in production emails | Trust drops because users see preview URLs | Email templates contain non-production domains |

The biggest business risk here is not just spam placement. It is failed onboarding, lower conversion from paid traffic, more support tickets asking "where is my code?", and wasted ad spend because users never reach activation.

The Fix Plan

My rule is simple: fix identity first, then volume. Do not start blasting more mail until authentication and alignment are correct.

1. Lock down the sending identity.

• Use one branded domain for all transactional mail.
• Prefer a dedicated subdomain like `mail.yourdomain.com` or `auth.yourdomain.com`.
• Make sure the visible From address matches that domain.

2. Repair DNS authentication in this order:

• SPF: authorize only the mail provider actually sending messages.
• DKIM: publish the selector records from your email provider exactly as given.
• DMARC: start with `p=none` so you can collect reports without blocking legitimate mail.

3. Clean up Supabase settings.

• Set SMTP credentials correctly in Supabase Auth if you are using custom SMTP.
• Replace any default sender names that look untrusted or generic.
• Confirm confirmation emails and password reset emails use production URLs only.

4. Fix template trust issues.

• Remove broken links, weird formatting, missing branding, and heavy image use.
• Keep subject lines clear and non-spammy.
• Avoid words that trigger junk filters unnecessarily, especially in early messages from a new domain.

5. Reduce send volume if needed.

• If you had a spike from ads or bots, rate limit signups and verification sends.
• Add basic anti-abuse controls on forms so one IP cannot hammer your inbox system.

6. Add monitoring before changing more code.

• Track delivery success rate by template type.
• Watch bounce rate daily for at least 7 days after changes.
• Set alerts if bounce rate exceeds 5 percent or complaint rate exceeds 0.1 percent.

7. Move cautiously on DMARC enforcement.

• Do not jump straight to `p=reject` unless you have confirmed all legitimate senders pass alignment.
• First collect reports for several days so you do not block real customers.

A practical DNS check can be done with a command like this:

dig txt yourdomain.com
dig txt _dmarc.yourdomain.com
dig txt selector1._domainkey.yourdomain.com

If those records are missing or duplicated incorrectly, I would fix that before touching anything else in the app.

Regression Tests Before Redeploy

Before I ship anything back into production, I want proof that deliverability improved without breaking signup flows.

Acceptance criteria:

• SPF passes for the production sending domain.
• DKIM passes for at least one real test message sent through production config.
• DMARC aligns with the visible From address.
• Test emails land in Gmail inbox or primary tab at least 8 out of 10 times across fresh accounts.
• Bounce rate stays under 2 percent during validation traffic.
• No staging links appear in any user-facing email template.
• Signup verification completes successfully on mobile and desktop.

Test plan:

1. Send to Gmail, Outlook, iCloud Mail, and one corporate mailbox if available. 2. Test both new user signup emails and password reset emails if both exist. 3. Open full headers and verify authentication results manually once per provider type. 4. Re-test after deployment from both desktop browser and mobile browser flows initiated by Lovable UI. 5. Confirm Cloudflare is not rewriting email links into broken redirects.

I would also run one negative test: submit invalid addresses through the funnel form to confirm anti-abuse controls stop obvious bot noise without blocking real users.

Prevention

Once this is fixed, I would put guardrails around it so it does not come back during future launches.

• Monitoring:
• Track delivery rates, bounces, complaints, open rates, and click rates weekly.
• Alert on sudden changes after ad campaigns go live.

• Code review:
• Review any change touching auth templates, environment variables, redirect URLs, or SMTP settings before deploy.
• Treat email config as production infrastructure code.

• Security:
• Store SMTP credentials in secrets only; never hardcode them in Lovable-generated files or client-side code.
• Restrict who can edit DNS records and Cloudflare settings using least privilege access.

• UX:
• Show clear "check your inbox" states after signup instead of leaving users confused when mail is delayed.
• Offer resend logic with cooldowns so users do not spam your own system by refreshing repeatedly.

• Performance:
• Keep email templates lightweight so they render fast on mobile clients too heavy on images can hurt engagement signals indirectly through poor user experience.

I also recommend keeping a short handover doc with current DNS values, provider names, verified sender domains, secret locations, and rollback steps. That saves hours when someone changes providers later under launch pressure.

When to Use Launch Ready

Use Launch Ready when you need this fixed fast without turning your funnel into a week-long engineering project.

This sprint fits best when:

• You already have a working Lovable plus Supabase funnel,
• Emails are being sent but landing in spam,
• You need production-safe fixes without rebuilding the product,
• You want monitoring plus handover so you can keep scaling after launch.

What I need from you before starting:

• Domain registrar access,
• Cloudflare access,
• Supabase project access,
• Access to your email provider account,
• A list of current sending domains,
• One example of an email that landed in spam,
• A short summary of where paid traffic comes from.

If you have paused ads because leads are not converting due to missed emails then this sprint pays for itself quickly because it protects every dollar spent on acquisition after launch day.

References

• https://roadmap.sh/cyber-security
• https://roadmap.sh/api-security-best-practices
• https://roadmap.sh/qa
• https://roadmap.sh/code-review-best-practices
• https://supabase.com/docs/guides/auth/auth-smtp
• https://support.google.com/a/answer/33786?hl=en
• https://dmarc.org/overview/

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Take the next step

If this is a problem in your product right now, here is what to do next:

• [Use the free Cyprian tools](/tools) - estimate cost, score app risk, check launch readiness, or pick the right service sprint.

• [Book a discovery call](/contact) - I will tell you honestly whether you need a sprint or if you can DIY the next step.

*Written by Cyprian Tinashe Aarons - senior full-stack and AI engineer helping founders rescue, launch, automate, and scale AI-built products.*