How to resolve email deliverability issues and 0% open rates in Protonmail inboxes?
Michael Ko
Co-founder & CEO, Suped
Published 18 Jul 2025
Updated 18 Aug 2025
7 min read
Dealing with 0% open rates in ProtonMail inboxes can be a frustrating experience. It often leaves senders wondering if their emails are even reaching the intended recipients or if there's a deeper deliverability issue at play. While it’s natural to suspect your emails are being blocked, the reality with ProtonMail is often more nuanced due to its strong focus on user privacy.
Unlike many other email providers, ProtonMail employs robust privacy features that can directly impact how open rates are tracked. This means a 0% open rate doesn't necessarily indicate an email delivery failure. Instead, it could be a sign that ProtonMail is actively stripping out tracking pixels or other mechanisms used by email service providers (ESPs) to record opens.
This guide will walk you through the common reasons behind low or 0% open rates in ProtonMail inboxes, help you differentiate between tracking issues and actual blockages, and provide actionable steps to improve your overall email deliverability.
Understanding Protonmail's unique filtering
One of the primary reasons you might observe zero open rates for ProtonMail recipients is their default privacy settings. ProtonMail automatically blocks tracking pixels, which are tiny, invisible images embedded in emails to detect when an email is opened. When these pixels are blocked, your email tracking system cannot record an open, even if the recipient views your message.
This commitment to privacy is a core tenet of ProtonMail's service, as detailed in their article on pixel tracking. Therefore, a reported 0% open rate for ProtonMail users might simply be a data anomaly, rather than a genuine deliverability problem. Focus instead on other engagement metrics like clicks, if available, which are less likely to be impacted by such privacy features.
It's also worth noting that ProtonMail does not publicly provide a dedicated postmaster site or specific remediation forms like some other major mail providers, making direct contact for deliverability issues challenging. This reinforces the need to ensure your email sending practices are robust and compliant across the board.
Understanding the issue
Many senders see 0% open rates and immediately assume their emails are being blocked or sent to spam. This can indeed be true for other providers, but for ProtonMail, it’s often a result of their privacy-focused approach, which strips out common tracking methods like pixels. This means recipients might be reading your emails without an open event being recorded by your sending platform. Therefore, a 0% open rate doesn't automatically mean 0% delivery.
Verifying actual delivery
To confirm if your emails are truly being blocked, rather than just having their open tracking suppressed, you should check for hard bounces. A hard bounce indicates a permanent delivery failure, meaning the email never reached the recipient's server or was rejected outright. If you are not seeing bounce messages for ProtonMail recipients, your emails are likely getting through, even if opens aren't being tracked. You can also send a test email to your own ProtonMail account to verify inbox placement directly.
Diagnosing true delivery blockages
If you've confirmed that emails are indeed bouncing or not reaching ProtonMail inboxes at all, the next step is to diagnose the underlying deliverability issues. ProtonMail, like other secure email providers, often has strict filtering mechanisms, especially for sender reputation.
A crucial step is to examine your email headers from a failed delivery. These headers often contain valuable information, including SMTP error codes and diagnostic messages that explain why an email was rejected. While ProtonMail doesn't have a postmaster site, these error messages are your best indicators for troubleshooting.
Common issues include being listed on a blacklist (or blocklist), poor domain reputation due to spam complaints, or a lack of proper email authentication. You can read more about diagnosing these problems in a general context by understanding how to diagnose and improve email deliverability.
Example of an Email Header
Received-SPF: pass (google.com: domain of example.com designates 192.0.2.1 as permitted sender) client-ip=192.0.2.1;
Authentication-Results: mx.google.com; spf=pass (google.com: domain of example.com designates 192.0.2.1 as permitted sender) smtp.mailfrom=user@example.com; dkim=pass header.i=@example.com; dmarc=pass(p=quarantine dis=none) header.from=example.com
X-Proton-Spam-Score: 5.0
Strengthening your email foundation
To ensure your emails are consistently delivered to ProtonMail and other mailboxes, focusing on core email authentication is paramount. This includes setting up and maintaining proper SPF, DKIM, and DMARC records. These protocols verify that your emails are legitimate and prevent spoofing, which significantly boosts your sender reputation.
Beyond authentication, maintaining a clean and engaged email list is critical. Regularly remove inactive subscribers and avoid sending to spam traps. This reduces bounce rates and spam complaints, both of which negatively impact your sender reputation. A degraded reputation is a common reason why emails might go to spam or be blocked by strict providers like ProtonMail.
Implement SPF: Ensure your SPF record lists all authorized sending IP addresses and domains. Incorrect SPF records can lead to emails being flagged as suspicious, even by providers like ProtonMail.
Set up DKIM: Use DKIM to digitally sign your emails, allowing recipients to verify that the email truly came from you and hasn't been tampered with. This is crucial for building trust.
Configure DMARC:Implement DMARC with a policy (e.g., p=quarantine or p=reject) to tell mailbox providers what to do with emails that fail SPF or DKIM authentication. This is foundational for strong email security and deliverability.
Clean your list: Regularly remove invalid or unengaged addresses. This improves your sender reputation and reduces the chances of hitting spam traps.
Monitor blocklists: Regularly check if your IP or domain is listed on any major email blocklists. Being on a blacklist will severely impact deliverability.
Ongoing monitoring and list hygiene
If you're still experiencing deliverability challenges, especially with a provider like ProtonMail that has strict filtering and no public postmaster forms, you might need to employ advanced strategies.
One key area is IP and domain warming, particularly if you are using a new or dedicated IP address. Gradually increasing your sending volume to a diverse set of recipients, including a small portion of ProtonMail users, helps build a positive sender reputation over time. You should also ensure your content is engaging and relevant to avoid spam complaints. Remember, even with advanced privacy features, ProtonMail still evaluates sender reputation to protect its users.
Typical email tracking
Mechanism: Relies on a 1x1 pixel image embedded in the email HTML. When the email is opened, this pixel loads, recording the event.
Data collection: Provides metrics like open rate, device used, and approximate location.
Providers: Common among most ESPs and mail clients, including Gmail and Outlook.
Protonmail's privacy features
Pixel blocking:ProtonMail automatically blocks known tracking pixels by default to protect user privacy.
Impact on metrics: Results in artificially low or 0% open rates for recipients, even if emails are delivered and read.
Focus on clicks: It's more reliable to gauge engagement through click-through rates, as clicks are typically not affected by pixel blocking.
Views from the trenches
Best practices
Always prioritize building a strong sender reputation through consistent authentication and good list management practices.
Segment your lists to send highly relevant content, improving engagement and reducing the likelihood of complaints.
Consider a slow and steady IP/domain warm-up if you are sending from new infrastructure.
Common pitfalls
Misinterpreting 0% open rates as 0% delivery; ProtonMail often blocks tracking pixels.
Neglecting email authentication (SPF, DKIM, DMARC) which is crucial for secure providers.
Failing to monitor bounce rates or email headers for actual delivery failures, not just open rate anomalies.
Expert tips
If your emails aren't bouncing, but you see 0% opens, it's likely a tracking pixel issue. Look at click-through rates as your true engagement metric.
ProtonMail's strict filtering means a clean sender history and proper authentication are more important than ever. Focus on quality, not just quantity.
Without a direct postmaster contact, your best bet is consistent adherence to email best practices. Test rigorously with a personal ProtonMail account.
Marketer view
Marketer from Email Geeks says they test with a ProtonMail inbox to verify if tracking pixels are being stripped out, as this is a common reason for reported zero open rates.
2025-01-01 - Email Geeks
Marketer view
Marketer from Email Geeks says that if bounce messages are not being received, it is less likely that emails are being fully blocked by ProtonMail. The low open rate might be due to tracking pixel blocking.
2025-01-02 - Email Geeks
Overcoming Protonmail deliverability hurdles
Resolving email deliverability issues and 0% open rates with ProtonMail inboxes often requires a dual approach. First, understand that reported 0% open rates are frequently a consequence of ProtonMail's privacy features, which block tracking pixels. In such cases, your emails are likely delivered, and you should focus on other engagement metrics, like clicks, to gauge effectiveness.
Second, if you're experiencing actual blockages or bounces, it points to deeper deliverability problems related to your sender reputation or authentication. By meticulously implementing email authentication protocols (SPF, DKIM, DMARC), maintaining a clean email list, and consistently sending valuable content, you can significantly improve your chances of reaching the inbox, even with privacy-focused providers.
ProtonMail inboxes can be a frustrating experience. It often leaves senders wondering if their emails are even reaching the intended recipients or if there's a deeper deliverability issue at play. While it’s natural to suspect your emails are being blocked, the reality with ProtonMail is often more nuanced due to its strong focus on user privacy.
Gmail and 
Outlook.
