Email Sending Health: Maintaining Great Rates & Recovering When Things Go Wrong

Email DeliverabilityEmail Sending Health: Bounces, Complaints & OpensThe three metrics inbox providers use to judge your emails — what each one means, how to keep them healthy, and exactly how to recover if they slip.

Overview

Your email sending health is determined by three key metrics that inbox providers use to judge whether your emails are wanted — and whether to deliver them. Keeping these metrics within healthy ranges ensures your emails reach your contacts' inboxes instead of their spam folders. This guide covers what each metric means, how to keep them at their best, and — if they slip — exactly how to recover.

1The Three Metrics That MatterInbox providers continuously evaluate your sending against these three benchmarks: MetricTargetWhat it meansBounce RateBelow 2%Percentage of emails that could not be delivered to the recipient's inboxSpam Complaint RateBelow 0. 1%Percentage of recipients who marked your email as spamOpen RateAbove 15%Percentage of delivered emails that were opened by the recipientTipAll three metrics are monitored continuously.

Even a short spike can affect your sending health, so it's best to build good habits from the start rather than react after the fact. 2Bounce Rate — Keep It Below 2%CausesWhat causes bounces?

• There are two types of bounces: Hard Bounce: The email address does not exist, the domain is invalid, or the recipient's server permanently rejected the email.
• Soft Bounce: A temporary issue — the inbox is full, the server was down, or the message was too large.

These can resolve on their own but repeated soft bounces become a problem.

How to Keep Bounce

Rate LowUse a verified opt-in process — only email people who confirmed their addressNever import purchased or scraped lists — these almost always contain invalid addressesRegularly clean your contact list — remove addresses that have not engaged in 6+ monthsUse an email verification tool before importing large listsRemove hard bounces immediately after each campaign — do not retry themAvoid sending to role-based addresses like info@, admin@, noreply@ — these bounce frequentlyHow to Recover If Bounce Rate Is HighStop sending campaigns to your full list immediatelyExport all contacts who have bounced and permanently suppress themRun your remaining list through an email verification service to identify other at-risk addressesRemove or suppress any address that hasn't opened an email in the last 90 daysResume sending to your most engaged segment only — those who opened in the last 30 daysGradually expand back to your broader list only after bounce rate returns below 2%Critical: Never Re-send to Hard Bounced AddressesHard bounced addresses should be permanently suppressed.

Re-sending to them signals poor list hygiene to inbox providers and will worsen your sending health. The platform automatically suppresses hard bounces — do not manually re-add them. 3Spam Complaint Rate — Keep It Below 0. 1%CausesWhat causes spam complaints?

Recipients do not remember signing up or did not consent to receive emailsEmail content feels irrelevant, unexpected, or too frequentThe unsubscribe option is hard to find or does not work properlyEmails look like phishing or are overly promotional in toneSending to old lists that were not engaged for a long timeHow to Keep Spam Complaint Rate LowAlways get explicit consent — never assume opt-inSend a clear welcome email immediately after someone subscribes so they recognise your nameMake the unsubscribe link large, visible, and working in every emailSet expectations upfront — tell subscribers what kind of content they'll receive and how oftenRespect unsubscribe requests immediately — never delay removalAvoid subject lines that feel deceptive, overly salesy, or misleadingMatch the email content to what the subscriber originally signed up forReduce frequency if engagement is dropping — over-sending is a leading cause of complaintsHow to Recover If Complaint Rate Is HighPause all bulk email campaigns immediately — even a few more complaints will worsen the situationIdentify which campaigns or segments are generating the most complaintsSuppress everyone who complained — do not email them againReview your opt-in flow to ensure consent is genuine and clearRewrite subject lines and email content to be less aggressive or misleadingAdd a highly visible one-click unsubscribe to every email going forwardResume sending only to your most engaged subscribers — people who opened in the last 30 daysMonitor complaint rate daily until it returns below 0.

1%Gmail & Yahoo Now Enforce Strict Complaint ThresholdsGmail treats a complaint rate above 0. 08% as a warning and above 0. 1% as critical. Yahoo Mail applies similar enforcement policies.

Sustained high complaint rates can result in your emails being bulk-foldered or blocked entirely. 4Open Rate — Keep It Above 15%FactorsWhat affects open rate? Subject line: The single biggest factor — unclear or generic subject lines dramatically reduce opensSender name: Recipients open emails from names they recognise and trustSend time: Emails sent at the wrong time for your audience will be buried or ignoredList quality: Disengaged contacts drag the open rate down — even if your content is greatPreview text: The short text shown next to the subject line in the inbox — often overlooked but influentialHow to Keep Open Rate HighWrite subject lines that are specific, curiosity-driven, or clearly valuable — avoid clickbaitPersonalise the subject line with the recipient's first name where appropriateKeep subject lines under 50 characters so they don't get cut off on mobileWrite a compelling preview text that complements the subject lineSend from a consistent, recognisable sender name — not a generic addressTest different send times — for most audiences Tuesday–Thursday between 9am and 11am performs wellSegment your list and send content that is relevant to each groupRe-engage or remove inactive subscribers regularly to keep your active list healthyHow to Recover If Open Rate Drops Below 15%Do not send to your full list — this will make the open rate worse, not betterIdentify your most engaged segment — contacts who opened at least one email in the last 60 daysSend a targeted re-engagement campaign to inactive contacts with a compelling offer or questionExample: "Are you still interested in hearing from us?

Click here to stay subscribed."Remove or suppress contacts who do not engage with the re-engagement campaignA/B test 2–3 different subject lines on a small segment before sending to your full listReview your email frequency — if you send too often, engagement dropsOnce open rate recovers above 15%, gradually expand sending to a broader audienceTip: Apple Mail Privacy ProtectionOpen rate is also affected by Apple Mail Privacy Protection (MPP), which pre-loads emails and registers them as 'opened'.

If a large portion of your audience uses Apple Mail, your open rate may appear higher than actual engagement. Focus on click rate as a secondary signal. 5Prevention Checklist — Best Practices at a Glance Best PracticeWhy it matters✓Only email contacts who explicitly opted inReduces bounces and spam complaints✓Send a welcome email immediately after sign-upSets expectations and builds recognition✓Clean your list every 90 daysRemoves dead addresses and inactive subscribers✓Include a visible, working unsubscribe link in every emailRequired by law and reduces complaints✓Verify email addresses before importing large listsPrevents hard bounce spikes✓Never re-add suppressed or hard-bounced addressesAvoids repeating damage to sender reputation✓Use a dedicated sending domainBuilds your own sender reputation over time✓Set up SPF, DKIM, and DMARC recordsProves email authenticity and improves deliverability✓Segment your audience and send relevant contentImproves open rate and reduces complaints✓Monitor your metrics after every campaignCatch problems early before they escalate6Quick Recovery ReferenceIf a metric slips, use this table to take the right action fast: SituationImmediate ActionNext StepBounce rate above 2%Pause campaigns.

Export and suppress all bounced addresses. Run list through email verification. Resume with engaged contacts only. Spam complaint rate above 0.

1%Pause all campaigns. Suppress all complainants immediately. Audit opt-in flow. Rewrite content and subject lines.

Add prominent unsubscribe. Open rate below 15%Stop sending to the full list. Identify active segment (opened in 60 days). Run re-engagement campaign.

Remove non-responders. A/B test subject lines. All three metrics are poorStop all email sending. Audit your entire list and consent records.

Start fresh with a verified, consented list. Warm up sending volume gradually. 7Frequently Asked QuestionsQ: How often should I check my sending metrics? Check your metrics after every campaign send.

For high-volume senders, review them daily. Catching a spike early is far easier than recovering from sustained damage. Q: Does a low open rate affect deliverability? Yes.

Inbox providers like Gmail and Outlook track engagement signals. If your emails are consistently ignored or not opened, they may begin routing future emails to the spam or promotions folder. Q: My bounce rate spiked after importing a new list — what do I do? Stop sending immediately.

Export all bounced addresses and suppress them. Run the remaining imported addresses through an email verification tool before sending again. Consider warming up the new list with a small segment first. Q: Is a 15% open rate realistic for all industries?

Open rate benchmarks vary by industry. B2B emails and transactional emails often see higher open rates (25–40%), while e-commerce promotional emails may see 10–20%. The 15% threshold is a general deliverability health signal — if your industry typically sees higher rates, aim for that higher standard. Q: Can I recover a damaged sender reputation?

Yes — but it takes time. Recovery typically involves suppressing problematic contacts, re-engaging only your warmest audience, and gradually rebuilding sending volume. Significant reputation recovery can take 4–8 weeks of consistent healthy metrics. Q: What's more important — open rate or click rate?

Both matter, but click rate is a stronger signal of genuine engagement — especially since open tracking can be inflated by privacy features like Apple Mail Privacy Protection. Use open rate as a top-of-funnel signal and click rate as the truer measure of subscriber interest. Q: Will pausing my campaigns hurt my sender reputation? No.

Pausing temporarily during a recovery is far better than continuing to send to a list that's generating bounces or complaints. Once you've cleaned your list and addressed the underlying issue, ramp back up gradually starting with your most engaged subscribers.