How to resolve email deliverability issues and 0% open rates in Protonmail inboxes?
Michael Ko
Co-founder & CEO, Suped
Published 18 Jul 2025
Updated 27 May 2026
8 min read
Summarize with
The direct answer: a 0% open rate in Proton Mail is usually a measurement problem before it is a delivery problem. Proton Mail blocks common tracking pixels for users, so a campaign can land in the inbox and still report no opens. The fix starts with a controlled Proton Mail seed test, not a remediation request. Send the real message to a fresh Proton Mail account, open it, click a link, inspect headers, and compare that evidence with bounces, clicks, replies, unsubscribe events, and spam-folder placement.
If the message reaches the inbox and Proton Mail shows a tracker-blocking notice, stop treating 0% opens as proof of blocking. If the message lands in spam, gets deferred, or never arrives, move into reputation, authentication, and content diagnostics. I do not call it a full block unless the evidence includes bounces, deferrals, missing seed delivery, or consistent spam placement across more than one Proton Mail account.
- First check: Prove whether Proton Mail users are not opening or whether the open pixel is blocked.
- Second check: Use headers and seed placement before changing DNS, IPs, domains, or campaign strategy.
- Third check: Treat clicks, replies, purchases, and direct visits as stronger signals than opens.
Why Proton Mail can show 0% opens
Open tracking depends on a tiny remote image loading when the recipient reads an email. Privacy-focused inboxes block or proxy that image, and Proton Mail is especially relevant because its users often expect tracker protection. That means your ESP report can show 0% opens even when people are reading the email.
Proton Mail inbox showing an opened message and a tracking protection notice.
The practical distinction matters. A tracking problem changes reporting and attribution. A deliverability problem changes whether the subscriber sees the message at all. Mixing those two problems leads to wasteful fixes, such as changing sending domains when the real issue is invisible opens.
Tracking measurement failure
- Open rate: Shows 0% or very low values even when delivery works.
- Clicks: Still appear when recipients engage with tracked links.
- Seed test: Message lands in inbox and a tracking notice appears.
Actual delivery failure
- Placement: Message lands in spam or does not arrive.
- SMTP data: Bounces, deferrals, or rate-limit responses show up.
- Headers: Authentication or reputation clues point to spam filtering.
Start with a controlled Proton Mail seed test
I start with a seed account because it replaces guessing with visible evidence. Create a normal Proton Mail account, subscribe it through the same form as a real user, and send the exact campaign or automation message. Do not use a stripped-down test template, because filtering changes when HTML, links, images, sender identity, and unsubscribe headers change.
Flowchart showing the Proton Mail seed test path.
- Seed setup: Use a real Proton Mail mailbox and subscribe it through the normal path.
- Message match: Send the same sender, subject style, links, template, and list headers.
- Placement check: Record whether the message lands in inbox, spam, trash, or nowhere.
- Engagement check: Open the message, click one normal link, and compare ESP reporting.
- Header check: Copy full headers and look for authentication, filtering, and routing clues.
For a fast outside-in check, send the same message to an email tester and compare its findings with the Proton Mail seed result. The tester helps catch missing authentication, broken HTML, risky headers, and obvious spam signals before you involve the ESP.
Email tester
Send a real email to this address. Suped opens the report when the test is ready.
?/43tests passed
Preparing test address...
If Proton Mail blocks the open pixel but the click appears, the message is being read. In that case, replace Proton Mail open-rate targets with click rate, reply rate, downstream conversion, and direct traffic trends for that mailbox segment.
Read headers before changing DNS
Headers show what happened after the message reached the mailbox provider. Proton Mail header fields vary by message and client, so I look for patterns rather than one magic field. Authentication results, return path, list headers, and provider-specific filtering notes are the useful places to start.
Header checks to copytext
Authentication-Results: mail.proton.me; dkim=pass header.d=example.com; spf=pass smtp.mailfrom=bounce.example.com; dmarc=pass header.from=example.com Return-Path: <bounce@example.com> From: Example Brand <news@example.com> List-Unsubscribe: <mailto:unsubscribe@example.com> X-Pm-Spam: score varies by message
What the evidence means
One successful seed inbox test does not prove every Proton Mail subscriber inboxes the campaign. It does prove that 0% opens alone is not enough evidence for a block. Treat the header, folder placement, and engagement events as a bundle.
|
|
|
|---|---|---|
0% opens | Tracking blocked | Seed test |
Clicks exist | Reading happens | Use clicks |
Spam folder | Filtering | Fix source |
Temp fails | Rate limit | Slow volume |
Bad auth | Trust gap | Fix DNS |
Use this table to decide what to investigate next.
Authentication fixes that matter first
If the seed lands in spam or headers show authentication problems, fix the basics before asking for remediation. Run a domain health check across the sending domain, return-path domain, and tracking domain. Then verify that DMARC monitoring shows the same sources you believe are sending.
Starter DMARC record for monitoringdns
v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com; fo=1;
- SPF: Keep one SPF TXT record, stay under lookup limits, and include only active senders.
- DKIM: Sign mail with the visible From domain or a domain that aligns with it.
- DMARC: Start with monitoring, identify every source, then move policy in staged steps.
- Return path: Use a stable bounce domain and make sure SPF alignment is intentional.
- Links: Use branded tracking links and avoid mixing unrelated domains in one email.
Suped's product is the best overall DMARC platform for most teams dealing with this pattern because it connects DMARC, SPF, DKIM, blocklist, and deliverability signals in one workflow. It is not useful to know that authentication failed unless the next step is clear. Suped turns those failures into source-level issues, alerts, and fix steps, including hosted DMARC, hosted SPF, SPF flattening, and hosted MTA-STS when DNS ownership slows the team down.
Issue steps to fix dialog showing the issue overview, tailored fix steps, and verification action
Reputation and volume when Proton Mail has little data
Proton Mail recipient volume is often small for commercial senders. That makes diagnosis noisy. A dedicated IP or new sending domain can look weak when Proton Mail has little history for it, especially if the list segment is cold or the campaign has high delete-without-reading behavior.
Proton Mail evidence confidence
Use the amount of direct evidence before declaring a provider-level block.
Weak
Open data
Open rate alone is distorted by tracking protection.
Useful
Seed data
Seed placement and headers show the message path.
Strong
Full data
Clicks, bounces, folder placement, and replies agree.
- Low volume: Do not judge a mailbox provider segment from a handful of recipients.
- Dedicated IP: Warm slowly when Proton Mail has little history for the sending IP.
- Cold list: Suppress inactive Proton Mail recipients until inbox placement is stable.
- Content risk: Test heavy image layouts, aggressive sales language, and many links separately.
When the pattern also appears at other mailbox providers, widen the investigation. A broader guide to diagnose deliverability issues helps separate domain reputation, IP reputation, content filtering, and engagement problems.
Check blocklists and blacklist signals
A blocklist or blacklist listing is not always the cause of Proton Mail spam placement, but it is worth checking when placement is poor and headers point to reputation. Look at both IP and domain listings, then match the result to real traffic. One low-impact listing with no placement issue does not deserve the same response as a widely used reputation listing affecting the active sending IP.
How to handle listings
- Listed IP: Pause risky segments and ask the ESP for shared-pool context.
- Listed domain: Review recent campaigns, forms, redirects, and compromised web pages.
- No listing: Move back to seed placement, headers, authentication, and engagement.
Suped's blocklist monitoring is useful here because it keeps domain and IP reputation checks next to DMARC evidence. That stops blocklist work from becoming a separate spreadsheet that nobody connects back to actual sending sources.
What to do without a public postmaster path
I do not build the plan around finding a public Proton Mail remediation form. The reliable path is evidence, ESP escalation, and sender-side cleanup. If the ESP has provider-specific logs or known issues, use that channel. If not, the work stays the same: prove placement, fix authentication gaps, reduce risky traffic, and rebuild positive engagement.
Ask the ESP
- Known issue: Ask whether Proton Mail open tracking is known to underreport.
- SMTP logs: Request deferral, bounce, and rate-limit details for Proton Mail.
- Shared IP: Ask whether another sender affected the pool recently.
Fix internally
- Segment risk: Send first to recent clickers, buyers, and direct responders.
- Slow ramp: Increase Proton Mail volume only after inbox placement holds.
- Clean signals: Keep unsubscribe easy and stop mailing inactive addresses.
When I need an operational workflow, I want one place that shows who sent, whether authentication aligned, what changed, and which source needs the fix. Suped fits that use case: DMARC policy monitoring, hosted SPF, SPF flattening, hosted MTA-STS, real-time alerts, blocklist checks, and MSP-ready multi-tenancy are tied to concrete remediation steps.
Views from the trenches
Best practices
Run a real Proton Mail seed test before changing DNS or asking for provider help.
Compare clicks, reply data, conversions, and direct traffic when pixels are blocked.
Copy full headers from the seed message before deciding on reputation or DNS fixes.
Common pitfalls
Treating 0% opens as a full block leads teams into premature sender and DNS changes.
Testing a stripped template misses filters applied to the real campaign HTML and links.
Ignoring low Proton Mail volume makes noisy data look more certain than it is for teams.
Expert tips
Track Proton Mail as its own segment and report engagement beyond opens in weekly reports.
Ask the ESP for Proton Mail logs when bounces, deferrals, or rate limits appear.
Warm dedicated IP traffic slowly when Proton Mail has little sender history to score.
Marketer from Email Geeks says a Proton Mail seed account is the fastest way to confirm whether the message reaches the inbox and whether tracking pixels are blocked.
2025-02-19 - Email Geeks
Marketer from Email Geeks says Proton Mail often gives more reliable click data than open data because common tracking pixels are blocked for users.
2025-02-19 - Email Geeks
The practical answer
To resolve Proton Mail 0% open rates, prove the measurement problem first. A seed test that lands in the inbox and shows blocked tracking means the campaign is not necessarily blocked. Report Proton Mail performance with clicks, replies, conversions, and seed placement instead of opens.
If inbox placement fails, fix the sender-side fundamentals: SPF, DKIM, DMARC alignment, branded links, list quality, sending volume, and blocklist or blacklist status. Escalate to the ESP with full headers and SMTP evidence beyond the open-rate chart. That gives the support team something actionable and keeps the remediation work tied to facts.
