Loops.so Bounce Rate Too High? Why Your Emails Are Failing (and How to Fix It)

You open your Loops.so dashboard expecting a “your account has been suspended” banner, because that’s how most email tools handle a bad bounce rate. It’s not there. Your campaigns are still sending. But your open rates have dropped, and Gmail’s Postmaster Tools (if you’ve set it up) shows your domain reputation sliding. That’s the trap with Loops: it doesn’t lock you out, so nothing forces you to notice the problem until deliverability has already degraded.

Loops is built for software companies (product updates, onboarding sequences and lifecycle email), and it leans on automation instead of hard account gates. That’s a different model from Brevo, Mailchimp or SendGrid, which can pause your sending outright. Here’s what Loops’ own documentation says about bounces, and why “no suspension” doesn’t mean “no problem.”

Loops Suppresses Bounces Instead of Pausing Your Account

Loops’ Reducing product email bounce rate guide lists what it handles automatically:

• Hard bounces (address or domain doesn’t exist, mailbox closed): the contact is added to suppression, so Loops stops sending to them.
• Soft bounces (mailbox full, server down, greylisted): Loops retries and tracks them separately.
• Complaints (someone marked your email as spam): treated like a hard bounce, so the contact is suppressed.

That’s convenient, because you don’t have to build your own suppression logic. But it also means there’s no forcing function. A provider that pauses your account is annoying, but it’s a loud signal that something needs fixing. With Loops, a rising bounce rate can sit there for weeks, degrading your sender reputation with Gmail, Yahoo and Outlook, before you go looking for it.

The Bounce Rate Guidance Loops Publishes

The same guide gives these benchmarks:

Spam complaints: Google’s sender guidelines say to keep the spam rate in Postmaster Tools below 0.1% and never reach 0.3%. Yahoo requires bulk senders to stay below 0.3%.

None of these numbers triggers a lockout inside Loops. Cross them, and Gmail and Yahoo’s spam filters do the suspending for you, invisibly, one send at a time.

Why This Matters More Since Google and Yahoo’s 2024 Bulk Sender Rules

If you send 5,000 or more messages a day to personal Gmail addresses, Google requires SPF, DKIM and DMARC authentication, plus one-click unsubscribe (RFC 8058 List-Unsubscribe headers) with unsubscribe requests honored within two days. Yahoo applies equivalent requirements. Loops signs your email with DKIM once your sending domain is set up, but it’s on you to finish the DNS setup and publish a DMARC record. Loops notes that failing DKIM or SPF pushes even soft bounces up, because mailbox providers hold or drop your mail.

Why Your Bounce Rate Is Climbing

Loops’ guide maps bounce reasons to causes, and it matches what we see:

• “Domain not found” bounces usually mean typo-filled or bot-submitted addresses from an unprotected sign-up form.
• “Mailbox does not exist” bounces usually mean stale addresses, often from an old imported list (a CSV, a CRM sync or a data-warehouse pull).
• “Blocked” bounces mean your sender reputation is low at that mailbox provider.
• Contacts who stopped engaging. Loops treats anyone who hasn’t opened in 60+ days as a bounce risk, because abandoned mailboxes eventually close or fill up.

Fixing It

1. Check your actual numbers. Loops won’t tell you to stop, so pull your bounce and complaint rates from the dashboard and compare them with the 2% and 0.1% lines above. If campaigns are over 5%, pause and work out which bounce reason dominates.

2. Confirm SPF, DKIM and DMARC are correctly configured, especially if you’re near Google and Yahoo’s 5,000-a-day threshold.

3. Narrow campaigns to engaged contacts. Loops recommends a segment of people active in the last 30 days (for example, a lastActive date property synced from your product) and advises against re-engagement campaigns to cold contacts. Keep the rest of the Audience, but stop mailing it.

4. Suppress permanently, don’t resync. Make sure whatever pipeline feeds Loops (Segment, a CRM sync, a nightly import) respects Loops’ suppression list instead of re-adding the same bad addresses.

A Note on List-Cleaning Services

Loops’ docs say plainly that they don’t recommend running your Audience through third-party verification or list-cleaning services. They argue that these tools produce false positives (valid mailboxes flagged as invalid), can create probe traffic, and don’t fix the upstream problem. Loops already suppresses hard bounces after the first one.

That’s a reasonable position for an Audience made of your own product’s users, and we’d follow it there. Where verification still fits with Loops’ advice:

• At the point of sign-up. Checking an address when the form is submitted is the “cleaner signup inputs” Loops asks for. It catches typos and throwaway inboxes before they become contacts.
• Before a large import from outside Loops, such as a list from an event or an old CRM that has never been mailed. Loops can’t suppress an address until it has bounced once. If you do verify, only remove addresses the service marks as invalid, and keep catch-all and unknown results, which avoids the false-positive problem.

Preventing It

Protect your sign-up forms. Loops recommends a captcha on every public form, bot protection at the edge, syntax validation on the client and server, and double opt-in for form submissions.

Block disposable domains with Loops’ email blocklist. Under Settings → Account, the blocklist accepts wildcard patterns that block a whole domain (Loops’ example blocks mailinator.com) and applies to every sign-up path (forms, API, CSV upload and integrations). Use our free disposable email checker to test a domain before you add it.

Validate in the same request as sign-up. Because Loops is API-first, most teams can call a real-time verification API in the same request as account creation, and reject undeliverable or disposable addresses before they’re sent to Loops.

Re-check authentication after any domain change. A migrated domain or a new sending subdomain is a common cause of a sudden bounce spike that has nothing to do with your list.

The Bottom Line

Loops won’t stop you from sending with a bad list the way Brevo or Mailchimp might. It suppresses each bad address after the first bounce and lets Gmail and Yahoo judge the rest. The published lines are clear (under 2% bounces, under 0.1% complaints), and the fix is upstream: protect your sign-up forms, block disposable domains, and send campaigns only to people who still engage.