How to improve email delivery rates to WP and Onet mailboxes?
Michael Ko
Co-founder & CEO, Suped
Published 23 May 2025
Updated 24 May 2026
9 min read
Summarize with
The direct answer is to treat WP and Onet as provider-specific delivery programs, not as ordinary recipient domains in a mixed campaign. I start by separating their recipients into their own queues, lowering hourly volume per IP, retrying temporary deferrals slowly, and proving that SPF, DKIM, DMARC, reverse DNS, complaint control, and list quality are clean before asking for higher acceptance.
For Onet, the common 4.7.1 deferral with #CR-IN-DEF-2 should be handled as a temporary rate or reputation pressure signal. It is not a cue to keep retrying at the same pace. For WP, the same operating model applies: isolate the traffic, slow it down, keep failure data by provider group, and make changes one at a time so the result is measurable.
Practical answer
A realistic WP and Onet plan starts with conservative throttling, not escalation. Paid delivery channels can help some senders, but they do not remove the need for authentication, low complaints, clean recipient data, and careful queue control.
Start with provider-specific throttling
The biggest mistake I see with WP and Onet is sending them inside the same job as Gmail, Microsoft, Yahoo, and smaller domains. That hides the provider-specific limit. A global campaign can look healthy while one local provider is quietly deferring or rejecting a growing share of the mail.
I split WP and Onet traffic by provider group, sending IP, sending domain, message stream, and campaign type. That lets me see whether a deferral starts after a predictable hourly count, after a content change, after an IP change, or after a complaint spike. Without that split, the sender usually guesses.
- Separate queues: send WP and Onet in their own jobs so retry behavior and throttles are isolated.
- Hourly caps: start below the suspected limit, then raise only after clean delivery cycles.
- Domain grouping: group related recipient domains under the same local provider when the MX path shows shared handling.
- One variable: change one factor at a time, such as rate, content, IP, or audience segment.
Starting throttles for WP and Onet testing
Use these as planning bands, then replace them with your own measured data.
Start
100-150/hour
Initial controlled test per provider group and IP
Watch
150-250/hour
Increase only if deferrals, bounces, and complaints stay low
Stop
250+/hour
Pause growth when temporary deferrals begin to cluster
Some senders report deferrals after roughly 200 to 300 messages per hour per IP, and paid channels have been discussed around low hundreds per hour rather than unrestricted bulk capacity. I treat those numbers as a caution sign, not a published rule. The right cap is the highest rate that stays stable for your own IPs, domains, content, and recipient mix.
Decode Onet temporary deferrals
The Onet response that matters most in this situation is a temporary deferral. The SMTP class 4.x.x means the receiving system is not accepting the message right now, but it has not issued a permanent rejection. Your MTA should retry, but the retry pattern needs to slow down.
Onet temporary deferral exampletext
4.7.1 <recipient@onet.pl>: Recipient address rejected: Sender address deferred by rule #CR-IN-DEF-2
I read that response as a provider rule telling the sender to reduce pressure. The specific internal rule name is less important than the behavior around it. If the rate goes down and the deferrals stop, you have a practical answer even without a postmaster explanation.
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|---|---|---|
4.7.1 | Temporary pressure | Back off |
#CR-IN-DEF-2 | Onet rule | Throttle |
5.x.x | Hard failure | Suppress |
Timeout | Connection pressure | Slow opens |
Compact interpretation of common WP and Onet delivery signals.
Do not hammer 4xx replies
Repeated fast retries after a temporary deferral add more connection pressure. I prefer longer backoff windows, fewer parallel connections, and a clear pause when deferrals cluster by provider.
Fix authentication before increasing volume
Before pushing more volume at WP or Onet, I verify that the domain has a boring, correct authentication setup. That means SPF passes for the visible sending path, DKIM signs every message with a stable selector, DMARC passes through SPF or DKIM alignment, and reverse DNS matches the sending infrastructure cleanly.
Run a real message through Suped's email tester before changing rate limits. Then use a domain health checker and continuous DMARC monitoring so authentication failures are visible by source, selector, and sending domain.
Minimum DNS authentication baselinedns
_dmarc.example.com TXT "v=DMARC1; p=none; rua=mailto:dmarc@example.com" example.com TXT "v=spf1 include:send.example.net -all" selector1._domainkey.example.com TXT "v=DKIM1; k=rsa; p=PUBLICKEY"
Email tester
Send a real email to this address. Suped opens the report when the test is ready.
?/43tests passed
Preparing test address...
The point is not to make DNS look perfect on paper. The point is to prove the actual message that enters WP or Onet has the same identity, envelope, headers, signing domain, bounce domain, and reverse DNS story every time. Inconsistent identity makes local throttles harder to debug.
Authentication checkpoint
- SPF: passes for the envelope sender and stays under DNS lookup limits.
- DKIM: signs the final message after all content and footer changes.
- DMARC: passes through aligned SPF or aligned DKIM for the visible From domain.
- rDNS: resolves cleanly and matches the sending host naming plan.
Build a WP and Onet sending plan
A good sending plan has a controlled route for each provider group. It defines the first cap, retry behavior, hold conditions, suppression rules, and the test window. I prefer boring send plans because they make the result obvious.
Flowchart showing a controlled WP and Onet delivery plan.
The plan should also separate transactional and marketing mail. Transactional streams need steadier acceptance, so I do not let a promotional spike consume the same hourly headroom. If both streams share an IP, the campaign queue should yield before the transactional queue starts receiving provider deferrals.
Mixed global campaign
- Visibility: provider-specific deferrals are buried inside global bounce data.
- Retries: the same retry policy hits every mailbox provider.
- Risk: one local throttle can create broad queue delays.
Provider-specific send
- Visibility: WP and Onet deferrals are measured by hour and source.
- Retries: backoff is tuned to the provider response pattern.
- Risk: local throttles stay contained within the local queue.
When a provider starts deferring, I do not immediately change content, IPs, and DNS at the same time. I lower the cap first. If the queue clears, the problem is capacity or reputation pressure. If the queue still fails at a low cap, I move to authentication, reputation, and content investigation.
Tune retries and queues
WP and Onet delivery problems often get worse because the sender treats a temporary deferral like a short network delay. That creates repeated attempts in a tight window. I prefer fewer parallel connections, a longer retry ramp, and an automatic hold when the same rule appears repeatedly.
Provider queue policy exampletext
provider_group = wp_onet max_connections = 1 max_messages_per_hour = 150 first_retry = 20m second_retry = 60m hold_if_4xx_rate_over = 20%
Those values are not universal limits. They are a clean starting point for testing. The important part is that the MTA has a separate policy for this provider group and the reporting can show when each threshold is crossed.
- Backoff: use longer retry intervals after repeated 4.7.1 responses.
- Connections: reduce parallel SMTP sessions for the provider group.
- Holds: pause campaign traffic when deferrals pass a defined percentage.
- Suppression: remove hard bounces and long-inactive recipients before the next test.
Reduce reputation pressure before asking for more
A sender that wants more WP and Onet volume has to look quiet and predictable. That means low unknown-user rates, low spam complaints, stable content, normal link domains, and a list that has recent engagement. If a campaign has a weak audience, increasing volume only makes the provider's filter more confident.
I also check blocklists and blacklists before escalating. A listing is not always the direct cause of a WP or Onet deferral, but it is a bad signal to bring into a postmaster conversation. Suped's blocklist monitoring is useful here because it ties IP and domain reputation checks into the same workflow as authentication monitoring.
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|---|---|---|
Bounces | Low | Rising |
Complaints | Rare | Clustered |
Engagement | Recent | Stale |
Listings | Clear | Listed |
Reputation checks to complete before increasing WP and Onet volume.
For related regional sending patterns, I treat Polish provider guidance and provider rate limits as separate workstreams. The first is about reputation and content expectations, and the second is about connection pacing and queue control.
Use postmaster escalation with evidence
Postmaster escalation works best after the sender has evidence, not guesses. I prepare a short packet that shows the sending IPs, domains, bounce samples, timestamps, message IDs, hourly volumes, authentication results, complaint controls, and the exact remediation already tried.
Escalation packet
- Identity: sending domains, envelope domains, DKIM domains, and IP addresses.
- Evidence: bounce samples with timestamps, response codes, and message IDs.
- Controls: current hourly caps, retry intervals, and suppression rules.
- Request: ask for the cause of the deferral and the safe volume range to test.
I do not treat paid delivery as a shortcut around sender quality. It can be part of the plan when the business case supports it, but the sender still needs queue discipline and clean authentication. Even paid channels usually have caps, and those caps still need measurement.
Where Suped fits
Suped's product fits this workflow because WP and Onet delivery issues rarely have one cause. A sender needs DMARC reporting, SPF and DKIM visibility, blocklist and blacklist checks, issue detection, and alerts in the same place. Suped brings those signals together so the team can see whether the problem is authentication, reputation, rate, or a specific source.
Issue steps to fix dialog showing the issue overview, tailored fix steps, and verification action
For most teams, Suped is the best overall DMARC platform because it turns raw authentication reports into issues, steps to fix, and alerts. Hosted SPF helps when sender lists change often. Hosted DMARC helps with policy staging. Hosted MTA-STS helps enforce TLS without web hosting. The MSP and multi-tenant dashboard helps agencies manage the same WP and Onet problem across many domains.
Manual workflow
The team collects bounce logs, DNS records, blocklist results, and DMARC XML files separately. That works for a one-off check, but it slows down repeat investigation.
Suped workflow
Suped combines authentication monitoring, issue detection, alerts, hosted records, blocklist visibility, and domain-level reporting in one operational view.
That does not replace provider-specific throttling. It gives the sender cleaner evidence and fewer blind spots before the rate test, during the retry window, and after a provider escalation.
Views from the trenches
Best practices
Segment WP and Onet into separate jobs so local throttles do not slow other recipients.
Treat 4xx responses as pressure signals and retry with longer backoff windows first.
Keep complaint, bounce, and inactive-recipient cleanup strict before volume increases.
Common pitfalls
Blending WP and Onet recipients into global campaigns hides provider-specific throttling.
Retrying too quickly after #CR-IN-DEF-2 turns a temporary deferral into pressure.
Assuming paid channels remove throttles leads to plans that exceed hourly caps later.
Expert tips
Start lower than expected, then raise hourly caps after several clean delivery cycles.
Track deferrals by provider group, IP, domain, campaign, and hour before changes.
Document every postmaster contact attempt with bounce samples and sending windows.
Marketer from Email Geeks says WP and related recipient domains need separate campaign batches with throttled sends over time.
2023-09-20 - Email Geeks
Marketer from Email Geeks says Onet 4.7.1 #CR-IN-DEF-2 should be treated as a temporary deferral that needs slower retries.
2023-09-20 - Email Geeks
My practical recommendation
If I had to improve WP and Onet delivery rates, I would not start by chasing a postmaster reply. I would first build a provider-specific queue, cap the hourly rate conservatively, slow retries after 4xx responses, clean the recipient segment, verify authentication on live messages, and watch deferrals by hour.
After that baseline is stable, I would raise volume in small steps. If the same threshold keeps producing deferrals, the sender has a real limit to plan around. If the threshold moves after authentication or reputation cleanup, the sender has found a fix. Either way, the answer comes from controlled delivery data, not guesswork.
