Hard + soft bounce combined. Above 5% Dotdigital throttles to protect IP reputation.
At a glance
The share of attempted sends that the receiving mail server rejected, hard plus soft combined. Above 5% Dotdigital’s compliance team will throttle, pause, or deliverability-coach the account to protect its shared-IP reputation. Above 8% the account risks a sending freeze. The single most important Dotdigital deliverability number; treat anything over 2% as a yellow flag and over 5% as a red one.
| What it counts | (numHardBounces + numSoftBounces) / numSent per campaign or programme send, rolled up across the period. The numerator and denominator both come from /v2/campaigns/{id}/summary and the equivalent programme endpoint. |
| Definition of “sent” | Accepted by Dotdigital’s outbound MTA, before the receiving server’s accept or reject decision. Each accepted send becomes one of: delivered, soft-bounced, hard-bounced, or deferred. |
| Hard vs soft split | Combined on this card. Hard bounces (invalid mailbox, domain non-existent, blocked sender) are auto-suppressed permanently after 1 attempt. Soft bounces (mailbox full, server temporarily unavailable, greylisted) are retried up to 5 times across 72h, then suppressed. To split the two, drill into the campaign view in Dotdigital. |
| Spam folder placement | Not counted as a bounce. A delivered-to-spam email is “delivered” from the sender’s point of view; the receiving server accepted it. Inbox-vs-spam placement is invisible to the sender unless you run a dedicated seed-list test (Dotdigital partners with EmailOnAcid and Litmus for this). |
| Reputation threshold | Dotdigital’s internal compliance threshold is bounce rate above 5% across the rolling 7-day window. Crossing this triggers an automatic notification to the merchant’s account manager and may result in throttled sending until the list is cleaned. |
| List-cleaning impact | A re-permissioning sweep (or a CSV upload to a new list) will spike bounce rate for 24 to 72h while invalid addresses get caught, then crash back to baseline. This is normal and not a red flag. |
| GDPR re-permissioning | Dotdigital’s quarterly inactive-contact suppression sweep typically removes 15 to 25% of the file. Bounce rate spikes briefly during the sweep then settles. |
| Time window | 30D vsP (rolling 30-day rate vs prior 30-day) |
| Alert trigger | >5%, drives the deliverability sentiment key |
| Sentiment key | klv_bounce_rate (shared with Klaviyo’s equivalent for cross-platform comparison) |
| Roles | owner, marketing, engineering |
Calculation
Calculated automatically from your Dotdigital data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.Worked example
A UK fashion retailer running on Magento with Dotdigital for the last 4 years. List size 412,000 consented contacts. The 30-day window covers 03 Apr 26 to 02 May 26.| Metric | Value |
|---|---|
| Total sends in period | 1,840,000 |
| Hard bounces | 22,100 (1.20%) |
| Soft bounces | 18,400 (1.00%) |
| Bounce rate (this card) | 2.20% |
- 2.20% is in the healthy band, well below the 5% throttle threshold. Industry baseline for established UK B2C lists with active hygiene is 1.5 to 2.5% on combined hard + soft.
- The 1.20% hard bounce rate would have been higher without Dotdigital’s auto-suppression. Each hard bounce only counts once because Dotdigital permanently removes that contact from sendable state after the first failure. Without auto-suppression, a stale list will compound bounces send after send.
- The retailer ran a Boxing Day catalogue upload on 26 Dec 25 that imported 38,000 contacts from a 2023 in-store loyalty CSV. For the first 3 sends in early January, bounce rate jumped to 6.8%. The Dotdigital deliverability team flagged the account, suggested running the file through Dotdigital’s Email Validation tool (which costs £0.005 per address), and bounce rate dropped back to 2.1% by 09 Jan 26. CSV uploads are the single biggest cause of unexpected bounce-rate spikes.
- Soft bounces concentrate at known free-mail providers. Roughly 40% of the 18,400 soft bounces came from
gmail.com(mailbox-full and greylisting),outlook.com(rate-limit deferrals), andyahoo.comaccounts. These mostly get retried successfully. - A 12 Apr 26 segment send to “Inactive 12m+” (62,000 contacts) bounced at 11.4%. This is what re-engagement campaigns look like, the Dotdigital recommendation is always to re-permission first, send second. The retailer paused the rest of the segment, sent a re-permissioning campaign, and only sent the promotional follow-up to those who clicked the consent link. Bounce rate on the second send: 0.8%.
Sibling cards merchants should reference together
| Card | Why pair it with Bounce Rate |
|---|---|
| Dotdigital Spam Complaint Rate | The other deliverability red-line. A spike in both at once means the list itself is the problem (stale or scraped). |
| Dotdigital Delivery Rate | The inverse view. 1 - bounce_rate ≈ delivery_rate minus deferrals. |
| Dotdigital Suppressed Contacts | The cumulative outcome of bounces. A rising suppression list means historic bounce hygiene worked, but the active sendable file is shrinking. |
| Dotdigital Active Subscribers Estimate | The real reachable base after suppressions. Pair to see “how much of my list is actually deliverable”. |
| Bounce Spike alert | The detection layer for sudden moves. This card shows the trend; the alert tells you when it broke. |
| Sender Reputation alert | Bounces feed sender reputation; a sustained high bounce rate trips this alert with a 24h lag. |
| Dotdigital Open Rate | Healthy bounce rate on a list with collapsing open rate is the spam-folder pattern; bounce rate alone won’t tell you. |
| BigCommerce Newsletter Signups | The supply side. A surge in low-quality signups from a paid campaign or a missing reCAPTCHA shows up here a week later. |
Reconciling against the vendor’s own dashboard
Where to look in Dotdigital: r1-app.dotdigital.com → Insights → Email Health for the rolling deliverability view. The Email Health dashboard splits hard vs soft and shows the receiving-domain breakdown (Gmail, Outlook, Yahoo, custom MX). Also useful: Account Settings → Email Sending Reputation for the IP-pool-level view that drives Dotdigital’s compliance team’s decisions. For a per-campaign forensic view: Campaigns → Reports → Campaign Summary → Detailed Statistics → Bounces. This breaks bounces down to the individual SMTP rejection code (e.g.550 5.1.1 mailbox does not exist).
Why our number may legitimately differ from Dotdigital’s dashboard:
| Reason | Direction of divergence |
|---|---|
| Soft-bounce retry counting. Dotdigital may count a soft bounce that retries successfully later in the period as “delivered” on its own dashboard but as “soft bounce + delivery” on the API summary, depending on the report variant. | Vortex IQ slightly higher on bounce rate |
| Time-zone. The Email Health dashboard runs on account locale; Vortex IQ runs UTC. Boundary-day spikes will appear in different 30-day windows. | ±0.1 to 0.3 percentage points at the boundary |
Region pod. Multi-pod accounts (r1 UK, r2 US, r3 AU) only count the connected pod. | Vortex IQ lower if pods exist outside the connected one |
| Suppression-list timing. Dotdigital removes hard-bounced contacts permanently on the next send attempt; if the merchant ran a fresh CSV upload after the API pull, the dashboard will show the post-suppression list and Vortex IQ the pre-suppression. | Small drift around CSV uploads |
| Card | Expected relationship | What causes legitimate divergence |
|---|---|---|
klaviyo.klv_bounce_rate | Same definition (combined hard + soft), comparable rate | A merchant migrating from Klaviyo to Dotdigital often sees bounce rate jump for the first 30 days because Dotdigital’s stricter soft-bounce retry policy surfaces existing list rot that Klaviyo’s longer retry window had been masking. |
mailchimp.mc_bounce_rate | Same shape, slightly lower threshold (4% Mailchimp, 5% Dotdigital) | Mailchimp’s compliance team intervenes one percentage point earlier. |
brevo_sendinblue.bs_bounce_rate | Same definition | Brevo also UK and EU shaped, similar GDPR profile, expect comparable rates on similar list sizes. |
Known limitations / merchant FAQs
My bounce rate just hit 6%. Will Dotdigital actually freeze my account? Not on the first crossing. Dotdigital’s compliance team will reach out (usually via the dedicated account manager for Engagement Cloud accounts; via thecompliance@dotdigital.com thread for self-serve). The first response is “tell us what changed”. Common answers: a CSV upload, a list import from another ESP, a long-dormant account resuming sending. Resolution paths in order of preference: (1) run the file through Dotdigital’s Email Validation tool, (2) re-permission inactive contacts, (3) reduce sending frequency to give the IP reputation time to recover. A second crossing within 14 days is more serious and may trigger a 24 to 48h sending pause.
Why is my bounce rate higher than my Klaviyo bounce rate was?
Two reasons, both structural. First, Dotdigital retries soft bounces only 5 times (Klaviyo retries up to 9 over 5 days), so addresses that Klaviyo eventually delivered to may bounce on Dotdigital. Second, the Dotdigital-published bounce rate combines hard + soft on a single line; Klaviyo also combines them, but the per-receiving-domain handling differs. Expect 0.5 to 1.0 percentage points higher on Dotdigital for the same list during the first 30 days post-migration; it converges as the list stabilises.
Hard vs soft, why does Dotdigital combine them on the dashboard?
Because in 2026 the receiving-server response codes have blurred. A 550 5.1.1 (mailbox doesn’t exist) is unambiguously hard, but 550 5.7.1 (policy rejection) might be a hard mailbox-blocked or a soft IP-blocked-this-hour. Dotdigital normalises these into hard or soft using its own classifier, but the combined number is the one that drives the IP-reputation feedback loop, so the headline metric merges them. The split is available in the per-campaign detailed statistics.
My account just imported a 50,000-row CSV. What do I do?
Run the file through Dotdigital’s Email Validation tool before sending. It costs roughly £0.005 per address (£250 for 50,000 contacts) and removes 5 to 15% of the file as undeliverable. The alternative, sending and bouncing, costs more in IP reputation than the validation fee.
A campaign to my “VIP customers” segment bounced at 8%. What’s wrong?
Almost certainly stale data. VIP segments are usually built from CRM exports of high-value customers who haven’t engaged with email for 6+ months. The CRM keeps the email address on file long after the contact’s mailbox has been recycled, transferred to a new domain, or auto-filtered to spam. Run the segment through Email Validation, then re-permission anyone over 12 months inactive before sending promotional content.
What counts as a “soft” bounce that retries vs one that gives up?
Dotdigital retries any soft bounce up to 5 times across 72 hours, then permanently treats it as a hard bounce and suppresses. After the suppression, future sends to that contact are blocked at the queue level (they don’t even reach the receiving server). Suppressions are stored on a per-account basis and exposed via Suppressed Contacts.
Does Apple Mail Privacy Protection (MPP) affect bounce rate?
No, MPP only affects open rate. Bounces are a server-to-server signal between Dotdigital’s MTA and the receiving mail server, and they happen before the email is rendered in any mail client. MPP does affect Open Rate, where Apple’s pre-fetch inflates opens, and it can indirectly affect engagement-based segmentation, which then affects who you send to, which then affects bounce rate. The chain is real but indirect.
My bounce rate is 0.8%, why is the alert still firing?
Check the Bounce Spike alert. The headline rate may be fine but the alert detects sudden moves vs a 30-day baseline (>2σ), so a campaign that bounced at 4% in a otherwise 0.8% account will trigger even though the rolling-30D rate stays low. The spike alert is a leading indicator; this card is the trend.
Should I worry about my bounce rate per-domain?
For mature brands sending more than 500k/month, yes. Healthy per-domain bounce rates: Gmail under 1.5%, Outlook under 2.5%, Yahoo under 3.0%, custom-domain (B2B) under 2.0%. A single domain spiking to 10%+ usually means an MX or DMARC change at that ISP, not a problem with your list. The per-domain breakdown is only available in the Dotdigital UI under Insights → Email Health.