Summary
Managing email deliverability and throttling with Cox.net requires a nuanced approach, particularly given their internal policies regarding IP reputation and sending volumes. Recent observations suggest that Cox.net (and other ISPs) may implement aggressive throttling measures, limiting the number of emails sent per minute or hour, often based on perceived sender reputation or even IP address geolocation.
Key findings
- Throttling effectiveness: Manually slowing down email sends to Cox.net, such as limiting to 25 messages per minute per connection for a domain, can significantly improve delivered message rates, sometimes by as much as 300%.
- IP geolocation impact: Cox.net has indicated that IP address geolocation can influence their throttling decisions, suggesting a need for careful consideration of sender infrastructure geography.
- Hourly limits: Some senders experience severe throttling, with limits as low as 5 to 25 email deliveries per hour, leading to rejections for any attempts beyond this threshold.
- Reputation weighting: Cox.net appears to heavily weight the reputation of neighboring IPs, even if they are associated with entirely different traffic, complicating deliverability for shared IP environments.
Key considerations
- Adjusting send rates: For Cox.net, implementing domain-specific (or connection-specific) rate limits can be highly effective. This involves explicitly configuring your sending system to send messages at a slower pace to Cox.net domains, as discussed in our guide on setting email domain connection limits for major ISPs.
- Monitoring deliverability: Continuously monitor your deliverability rates, including delivered, bounced, and deferred messages, to identify throttling patterns and adjust sending strategies accordingly. This aligns with overall email deliverability best practices.
- IP pool management: Consider the impact of shared IP pools on your reputation, especially if Cox.net is factoring in neighboring IP reputation. Dedicated IPs might offer more control, though slow warming is still crucial. Learn more about managing email deliverability for large sends.
- Treating Cox.net like Yahoo: Given that Cox.net email addresses are now managed by Yahoo, senders should adhere to Yahoo's bulk email restrictions and guidelines.
What email marketers say
Email marketers often share experiences and strategies for dealing with ISP-specific challenges like throttling. For Cox.net, the consensus points towards active management of sending rates and a keen awareness of how their systems evaluate sender trustworthiness. The practical insights from fellow marketers can be invaluable for real-world application.
Key opinions
- Successful throttling: Marketers have seen significant success by manually adjusting sending speeds to Cox.net, validating that slower rates can lead to higher delivery rates.
- Geolocation and reputation: There's a strong belief that Cox.net considers IP address geolocation and the reputation of neighboring IPs, making shared IP environments particularly challenging.
- Unclear 'suspicious' score: Some marketers express confusion about Cox's internal 'suspicious' sender scoring, as even pristine, white-hat campaigns can be subject to strict limitations.
- Severe hourly limits: Experiences of being limited to 5-25 emails per hour highlight the extreme throttling Cox.net can impose on affected senders.
Key considerations
- Test custom throttling: Marketers should experiment with specific sending rates for Cox.net (e.g., 25 messages/min/connection) to find the optimal balance between delivery speed and deliverability. This is a practical step to prevent email throttling and delays.
- Review IP reputation: If using shared IPs, investigate your IP's reputation and consider if neighboring sending behavior is impacting your deliverability to Cox.net. Regularly checking for blocklist status is a good proactive step.
- Patience with large pools: While manual throttling works for small IP pools, marketers acknowledge that it might be a slower process for larger pools, requiring sustained testing.
- Align with new ISP policies: Marketers should stay updated on major ISP policy changes, such as Google and Yahoo's new rules for bulk email senders, as these often influence practices for other providers like Cox.net. General deliverability issues are often linked to these changes, as described in email deliverability best practices.
Email marketer from Email Geeks suggests that by applying a very slow mailing speed, such as 25 messages per minute per connection for the Cox.net domain, they observed a significant increase in the delivered message rate, factoring in bounces and transient errors. This indicates that Cox.net responds favorably to reduced sending velocity.
Email marketer from Email Geeks states that even with a 'turtle speed' of sending, all messages to the Cox.net network from a small dedicated IP pool were delivered within one hour. This makes the slower sending rate a viable strategy without excessive delays for smaller volumes.
What the experts say
Email deliverability experts offer strategic guidance rooted in extensive experience with ISP policies and email ecosystem dynamics. Their perspectives often highlight the importance of proactive reputation management, technical compliance, and adaptive sending practices to navigate complex throttling mechanisms employed by providers like Cox.net.
Key opinions
- Sender reputation is paramount: Experts consistently emphasize that a strong sender reputation is the cornerstone of avoiding throttling and ensuring high deliverability.
- Gradual sending (warmup): Warm-up new IPs or domains gradually to build trust with ISPs, a process critical for large sends.
- Authentication standards: Proper implementation of SPF, DKIM, and DMARC is non-negotiable for establishing sender legitimacy.
- Engagement metrics matter: ISPs (like Cox.net via Yahoo) use user engagement signals (opens, clicks, complaints) heavily to determine sender reputation and apply throttling.
Key considerations
- Proactive monitoring: Utilize monitoring tools to track your IP and domain reputation across various blocklists and ISPs to detect issues early, a core part of diagnosing email deliverability issues.
- Segment sending: For specific ISPs like Cox.net or Yahoo, consider segmenting your audience and sending at adjusted rates to avoid triggering throttling mechanisms. This is akin to strategies used for Yahoo's throttling.
- List hygiene: Regularly clean your email lists to remove inactive or invalid addresses, as high bounce rates negatively impact your sender reputation and can lead to throttling. This is a common best practice to avoid email throttling.
- Feedback loop participation: Sign up for ISP feedback loops to quickly identify and remove users who mark your emails as spam, preventing further reputation damage.
Expert from SpamResource.com highlights that effective email deliverability hinges on maintaining a pristine sender reputation, which is built on consistent positive sending behavior over time. ISPs like Cox.net prioritize trusted senders.
Expert from Wordtothewise.com suggests that ISPs often implement greylisting or temporary rejections as a first line of defense against suspicious senders, forcing legitimate senders to retry, and illegitimate ones to give up. Throttling by Cox.net might leverage similar principles.
What the documentation says
Official documentation and widely accepted best practices provide the foundational knowledge for navigating ISP deliverability challenges, including throttling. While specific, granular details on Cox.net's internal algorithms are often proprietary, general guidelines from prominent industry bodies and ISPs themselves offer actionable advice for senders.
Key findings
- Compliance with standards: Documentation consistently stresses adherence to internet standards (RFCs) and email authentication protocols (SPF, DKIM, DMARC).
- List quality emphasis: ISPs (and their documentation) highlight the critical role of maintaining clean, opted-in email lists to reduce bounces and spam complaints.
- User engagement: Many ISP guidelines suggest that positive user engagement (opens, clicks) helps build sender reputation, while negative engagement (complaints, unsubscribes) can lead to filtering or throttling.
- Avoiding spikes: Documentation often warns against sudden, large volume increases from new or unestablished sending IPs without proper warm-up.
Key considerations
- Adhere to sending limits: While Cox.net's specific limits might not be fully public, general documentation advises respecting implied or explicit sending rate limits to avoid triggering throttling, and to be prepared for throttling from various email clients.
- Implement authentication: Ensure your SPF, DKIM, and DMARC records are correctly configured and aligned. A complete guide to DMARC, SPF, and DKIM explains the importance of these protocols.
- Monitor blocklists: Regularly check if your sending IPs or domains are listed on any major blocklists, as this will severely impact deliverability to Cox.net and other ISPs. This is part of the best practices for email deliverability.
- Understand ISP policies: Be aware that Cox.net's email services are integrated with Yahoo, meaning senders should also consider Yahoo's specific guidelines and restrictions for bulk email, as outlined in recent updates regarding Google and Yahoo's new bulk sender rules.
Documentation from Cox Automotive Retail advises monitoring the number of emails sent and received to maintain good deliverability. This proactive approach helps in identifying potential throttling triggers before they severely impact campaigns.
Documentation from Campaign Refinery suggests spacing out email sends rather than sending all emails at once. This strategy aligns with managing throttling and preventing ISPs from perceiving sudden bursts of email as suspicious.
