accepted is the easy part. Getting that email into the inbox — and keeping it that way over time — depends on how you manage your domain, your lists, and your sending behavior. This page covers the practices that matter most, plus what Helo specifically expects and enforces.
We care a lot about deliverability, and we work hard to keep our sending infrastructure in good standing — but inbox providers are ultimately judging your domain and your sending habits, not just ours. So think of it as a team effort, we’re in this together!
Authenticate your sending domain
Inbox providers use authentication to decide whether a message is really from who it claims to be from. Unauthenticated mail is far more likely to be filtered as spam, regardless of content quality.- SPF and DKIM are set up automatically when you verify a sending domain with Helo — DKIM signing is configured for you, and we provide the records you need to add.
- DMARC tells receiving servers what to do when a message fails SPF/DKIM alignment, and gives you visibility into who’s sending on your domain’s behalf. Helo doesn’t create a DMARC record for you, so add one yourself at your DNS provider. Start with a monitoring policy (
p=none) to collect reports without affecting delivery, then move top=quarantineorp=rejectonce you’re confident all legitimate mail from your domain is passing. - Use a custom Return-Path (covered in domain setup) so SPF aligns with your From domain — this is required for strong DMARC alignment.
Protect your domain and IP reputation
Reputation is the biggest factor in inbox placement, and it’s earned (or lost) over time based on how recipients and inbox providers respond to your mail.- Warm up new domains gradually. A domain with no sending history that suddenly sends thousands of messages looks suspicious to inbox providers. Start with smaller volumes to your most engaged recipients and ramp up over days or weeks.
- Avoid sudden volume spikes. Even an established domain can see deliverability dip if it sends a much larger broadcast than usual. See delivery rate for how Helo paces large sends.
- Watch engagement, not just delivery. Opens, clicks, and replies signal to inbox providers that recipients want your mail. Consistently low engagement — even without hard bounces or complaints — can quietly hurt inbox placement over time.
- Because Helo uses separate infrastructure for transactional and broadcast mail, a reputation hit on one doesn’t automatically affect the other — but poor practices anywhere on your account still reflect on you as a sender.
Keep your list clean (list hygiene)
Every address you send to should be one you have a good reason to be emailing.- Use opt-in, not purchased or scraped lists. Recipients who never asked to hear from you are far more likely to mark your mail as spam. Double opt-in (confirming a subscription via a follow-up email) further reduces invalid addresses and complaints.
- Remove hard-bounced and unengaged addresses. Helo automatically suppresses hard bounces, but you should also periodically prune subscribers who haven’t opened or clicked in a long time (for example, 6–12 months), especially before a large campaign.
- Validate addresses at capture. Catching typos and fake addresses at sign-up (via client-side validation or a verification service) prevents them from ever reaching your list.
- Segment by engagement and consent, not just demographics — sending broadcasts only to people who actually want them is the single biggest lever you have over your complaint rate.
Always include unsubscribe links
Every broadcast must include a way to opt out — this isn’t just best practice, it’s a legal requirement in most jurisdictions (e.g. CAN-SPAM in the US, CASL in Canada, GDPR/PECR in the EU/UK). Helo automatically adds unsubscribe links andList-Unsubscribe headers to your broadcast messages, so you don’t need to build this yourself.
When someone unsubscribes, Helo adds them to your suppression list for that mail type immediately — honor unsubscribe requests promptly and never re-add someone who has opted out without fresh, explicit consent.
Mind your sending volume
Sending too much, too fast, or to too many unengaged addresses at once is one of the most common causes of deliverability problems:- Large broadcasts are processed gradually by design — see delivery rate for estimated processing times by list size.
- If you expect a significant, sustained increase in your normal sending volume, reach out to us beforehand so we can help you plan the ramp-up. Sudden, sustained spikes are one of the fastest ways to damage domain reputation, and that’s true regardless of how well-behaved your list is.
- Prefer sending consistently (e.g. a weekly newsletter) over irregular bursts — predictable patterns are easier for inbox providers to trust.
Helo’s bounce and spam rate thresholds
Helo actively monitors deliverability signals per Channel and will alert you — or suspend sending — if they cross unsafe thresholds:
These mirror the thresholds major inbox providers (Gmail, Yahoo) use to judge sending behavior — see deliverability alerts for details. Consistently exceeding them risks not just a Helo suspension, but real damage to your domain’s reputation with inbox providers that outlasts any one platform.
If a Channel is suspended for exceeding these thresholds, sending is paused until the underlying issue (typically list hygiene or a compromised sign-up form) is addressed. Contact us if you’re approaching a threshold and want help getting ahead of it — we’d much rather help you fix the cause than suspend your account.
Migrating to Helo from another ESP
If you’re moving from another email service provider, a few precautions will help you preserve the sending reputation you’ve already built and avoid deliverability issues during the switch:- Set up a new domain (or subdomain) for Helo, or re-verify DNS carefully. Sending reputation is tied to your domain and IPs, not to a specific provider. Add Helo’s DKIM and Return-Path records, and update your SPF record to include Helo alongside (or in place of) your previous provider while both are active. Do not remove your old provider’s SPF/DKIM records until you’ve fully cut over.
- Import only engaged, opted-in recipients. Don’t bulk-import your entire historical list — carry over addresses that have opened or clicked recently. Sending a first broadcast to years of accumulated, unengaged addresses is one of the most common causes of a bad start on a new platform.
- Bring over your suppression list. Export bounced, complained, and unsubscribed addresses from your previous ESP and add them to Helo’s suppression list via the API or dashboard before you send anything, so you don’t re-contact people who already opted out elsewhere.
- Warm up before cutting over completely. Run Helo in parallel with your existing provider for a period, gradually shifting volume over rather than moving 100% of your sending in one day — especially for a new domain or subdomain with Helo.
- Test first. Use a Sandbox Channel or test mode to validate your integration, templates, and webhook handling before sending to real recipients.
- Compare like-for-like metrics. Bounce and complaint definitions vary slightly between providers, so expect some settling time before you can meaningfully compare rates against your historical baseline.