How to improve email delivery rates to WP and Onet mailboxes?
Michael Ko
Co-founder & CEO, Suped
Published 23 May 2025
Updated 17 Aug 2025
9 min read
Email deliverability can be a complex challenge, and some mailbox providers are particularly stringent. WP and Onet, two prominent Polish email services, are known for their strict email filtering and throttling practices. Many senders encounter significant hurdles when trying to achieve high delivery rates to these inboxes. Unlike many global providers, they often operate with unique rules and low volume limits, making it essential to adapt your sending strategy.
The challenges with WP and Onet mailboxes are not uncommon. Senders often struggle to get higher volumes delivered reliably, and contacting their postmaster teams for assistance can be difficult. This often leads to messages being throttled or outright rejected, even for legitimate mail. To successfully reach users on these platforms, a tailored approach focusing on technical configurations, sender reputation, and content quality is crucial.
This guide will walk you through the specifics of improving your email deliverability to WP and Onet, covering the unique aspects of these providers and offering actionable strategies to help your emails land in the inbox.
Understanding WP and Onet's unique challenges
Polish mailbox providers like WP.pl and Onet.pl have distinct policies that set them apart from major international players such as Gmail or Outlook. These differences primarily revolve around their aggressive anti-spam measures, often resulting in severe throttling and filtering of incoming mail. Senders often report that these providers prioritize local traffic and can be less responsive to inquiries from foreign entities, making troubleshooting complex.
One common issue is encountering specific bounce codes. For instance, you might see a bounce message like 4.7.1 <recipient@onet.pl>: Recipient address rejected: Sender address deferred by rule #CR-IN-DEF-2. This specific error indicates that the sender's address has been temporarily deferred by an internal Onet.pl rule, often related to volume limits or suspicious sending patterns. Understanding these unique characteristics is the first step toward better deliverability. You can learn more about the specifics of Polish mailbox providers in this article.
Both WP and Onet, along with other Polish providers like Interia, are known to offer what they term 'premium delivery' programs. These programs allow senders to pay a monthly fee in exchange for higher accepted volumes. However, even with these paid services, the volume increases can be minimal. Reports suggest that without such a program, typical limits before encountering deferrals might be as low as 200-300 emails, while premium channels might allow around 500 emails per hour per IP. This highlights that even paid programs offer controlled, limited volume rather than open access.
Given these strict limitations, a blanket sending strategy that works for other major providers will likely fail for WP and Onet. Senders must be prepared to implement more granular control over their outgoing mail, focusing on precise throttling and meticulous list management. This requires continuous monitoring and a willingness to adjust practices based on observed bounce rates and delivery reports. Patience is a virtue when dealing with these unique local ecosystems.
Foundation of good deliverability
While WP and Onet present unique hurdles, the fundamental pillars of email deliverability remain essential. Strong email authentication, a solid sender reputation, and a healthy mailing list form the bedrock upon which any advanced strategy must be built. Without these in place, even the most sophisticated targeting will fall short.
Ensuring your domain and sending infrastructure are properly authenticated is non-negotiable. This includes correctly configuring SPF, DKIM, and DMARC records. These protocols verify that your emails are legitimately coming from your domain, preventing spoofing and building trust with mailbox providers. Misconfigured or missing records are red flags that can immediately lead to messages being rejected or routed to the spam folder, especially by strict providers like WP and Onet.
Sender reputation is another critical factor. This encompasses your IP and domain history, bounce rates, spam complaint rates, and engagement metrics. A poor reputation signals to mailbox providers that your emails might be unsolicited, triggering their spam filters. Regularly cleaning your email lists of inactive or invalid addresses, avoiding purchased lists, and focusing on sending to engaged recipients can significantly boost your reputation and improve overall deliverability. Maintaining a positive sender reputation is particularly important for Polish providers.
Beyond technical setup, the quality of your email content and the engagement of your audience play a substantial role. Personalized, relevant content that genuinely interests your subscribers reduces spam complaints and increases opens and clicks. This positive engagement signals to providers that your emails are valuable, further enhancing your sender reputation. For a comprehensive overview, explore how to boost email deliverability rates.
Technical setup
SPF records: Ensure all legitimate sending IP addresses are included.
DKIM signatures: Properly sign your outgoing emails.
DMARC policy: Implement a policy (even p=none) to monitor and enforce authentication.
PTR records: Ensure your sending IPs have reverse DNS configured correctly.
Sender practices
List hygiene: Regularly remove inactive or bouncing addresses.
Content quality: Avoid spam trigger words and ensure relevance.
Engagement monitoring: Focus on sending to engaged subscribers.
Sender reputation: Cultivate a positive history with consistent, desired sending.
Strategies for high-volume senders
For high-volume senders, navigating WP and Onet requires careful strategy beyond basic authentication. The key lies in understanding and respecting their low daily volume thresholds, even for senders with excellent reputations. Ignoring these limits will almost certainly lead to throttling or, worse, your IP or domain being added to an internal blocklist.
A crucial strategy is to implement strict throttling and segment your email sends specifically for Polish providers. Instead of sending large batches, distribute your emails to WP and Onet recipients over longer periods. This gradual approach helps build trust and avoid triggering their volume-based filters. You might consider isolating your Polish recipients into a dedicated send stream, separate from your main campaigns.
Engagement monitoring for these specific domains is also vital. If users are not opening or clicking your emails, it signals low interest to the mailbox provider, which can negatively impact your deliverability. Regularly prune inactive subscribers from your lists, especially those on WP and Onet. Focus on re-engagement campaigns or remove unengaged subscribers to protect your sender reputation and reduce spam rates. If you notice your emails going to spam, consider reducing volume and improving engagement.
For extremely high volumes, engaging with local Polish email service providers (ESPs) that have pre-existing relationships and 'premium delivery' agreements with WP and Onet may be a viable, albeit costly, solution. These local providers often have established whitelists and direct contacts, making it easier to bypass some of the standard throttling. However, be aware that even these agreements come with strict volume ceilings.
Recommended sending volumes (approximate)
Initial warm-up: Start with 50-100 emails per IP per hour for new domains.
Standard sending (non-premium): Aim for 200-300 emails per IP per hour, or even lower if issues arise.
Premium delivery: Max 500 emails per IP per hour. Requires direct agreement.
Daily limits: These hourly rates generally apply. Adjust based on bounce logs.
Monitoring and adaptation
Achieving consistent email delivery to WP and Onet is not a one-time setup, but an ongoing process that requires diligent monitoring and continuous adaptation. Given their dynamic filtering rules and strict volume controls, staying informed about your sending performance is paramount.
Regularly monitor your bounce rates, especially the specific deferral codes you receive from WP and Onet. Tools that provide granular bounce reporting are invaluable. For example, if you see an increase in #CR-IN-DEF-2 errors from Onet, it's a clear signal to reduce your sending volume or adjust your throttling. Pay close attention to your sender reputation metrics as well, as a decline can quickly lead to stricter filtering. For general guidance on improving email deliverability, you can consult our guide on improving email delivery to Polish users.
Additionally, being aware of global changes in email deliverability, such as new sender requirements from major providers, can indirectly impact your standing with smaller, regional providers. While WP and Onet might not explicitly publish such detailed guidelines, adhering to broader industry best practices for avoiding spam filters will always serve you well. Proactive monitoring helps you quickly identify and address issues, preventing them from escalating into long-term blocklist problems. You can learn more about what happens when your domain is blocklisted.
Performing regular email deliverability tests is also a good practice. By sending test emails to various WP and Onet addresses, you can gain insights into how your messages are being treated. This allows you to spot potential issues before they affect your entire campaign. Consistent effort in these areas will yield better results over time.
Views from the trenches
Best practices
Implement specific, conservative throttling limits for emails destined for WP.pl and Onet.pl addresses, treating them as distinct segments.
Ensure your SPF, DKIM, and DMARC records are impeccably configured and actively monitored for proper authentication and alignment.
Prioritize strict list hygiene, regularly removing unengaged subscribers and invalid email addresses from your mailing lists.
Focus on sending highly relevant and engaging content to reduce the likelihood of spam complaints and increase positive engagement metrics.
Common pitfalls
Sending large, untargeted volumes to WP or Onet mailboxes, which almost always triggers their strict throttling and filters.
Neglecting to properly authenticate your emails, leading to immediate rejection or spam folder placement by these vigilant providers.
Ignoring specific bounce messages like the '4.7.1 #CR-IN-DEF-2' error, which provides crucial clues about delivery issues.
Treating Polish mailbox providers the same as global providers, failing to acknowledge their unique, more restrictive policies.
Expert tips
Actively seek and maintain direct communication channels with postmaster teams for challenging providers, even if responses are infrequent.
Use granular bounce data and email logs to precisely identify the specific reasons for rejections or deferrals from WP and Onet.
Experiment with different sending patterns and IP allocations to identify the optimal approach for these sensitive mailboxes.
Research and understand local email marketing regulations and cultural nuances that might influence email acceptance in Poland.
Expert view
Expert from Email Geeks says that Polish providers like WP and Onet are notoriously difficult for high-volume email sending, often requiring senders to significantly throttle their email campaigns and segment their recipient lists.
2023-09-21 - Email Geeks
Marketer view
Marketer from Email Geeks says they frequently encounter the specific bounce error '4.7.1 Recipient address rejected: Sender address deferred by rule #CR-IN-DEF-2' when sending to Onet.pl, and information on this rule is hard to find.
2023-09-21 - Email Geeks
Navigating Polish mailboxes for better delivery
Improving email delivery rates to WP and Onet mailboxes is undoubtedly challenging, but it is achievable with a disciplined and adaptive approach. The key lies in recognizing their unique nature as highly localized and stringent providers, demanding more attention than global counterparts.
By focusing on impeccable email authentication, maintaining a robust sender reputation through consistent engagement and clean lists, and implementing strict volume throttling, you can significantly enhance your chances of inbox placement. While direct postmaster communication might be difficult, persistent monitoring and adjustment of your sending patterns based on bounce data will provide the insights needed to succeed. Treat these providers with the respect their unique filtering systems demand, and you will see your deliverability improve over time.
