Summary
Experts, marketers, and documentation sources offer a mixed view on whether a DNS outage impacts email deliverability when sends are paused and resumed. While some experts believe ESPs caching mechanisms should mitigate major issues, others and numerous marketers emphasize the potential for temporary bounces, delayed deliveries (related to TTLs), and indirect effects on sender reputation through increased complaints or bounces. Technical documentation highlights DNS propagation delays, the complexities of DNSSEC, and the role of retry mechanisms. The prevailing advice centers on cautious resumption of sending, proactive monitoring of engagement metrics, and careful assessment of inbox placement.
Key findings
- ESPs Caching: ESPs typically cache DNS records, mitigating impact, but effectiveness varies.
- Temporary Issues: Expect temporary spikes in bounces and potential delivery delays.
- Reputation Risk: Increased complaints or bounces can negatively affect sender reputation.
- Propagation Delays: DNS changes can take up to 48 hours to propagate, impacting immediate resumption.
- Monitor Engagement: Carefully monitor engagement metrics (opens, clicks) after resuming sends.
- IP Address Reputation: When there is a long pause it can impact your IP address, which can lower email placement rates and you will need to warm up your IP address again.
Key considerations
- Gradual Resumption: Gradually increase sending volume to re-establish sender reputation.
- Monitor Bounce Logs: Proactively monitor bounce logs for increased errors after the outage.
- Check Inbox Placement: Assess inbox placement to identify deliverability issues.
- Consider DNSSEC: If DNSSEC is enabled, verify proper record validation.
- Check Feedback Loops: Closely watch feedback loops for increased complaint rates.
- Be Patient: Allow sufficient time for DNS records to propagate before resuming sending and to test deliverability.
What email marketers say
10 marketer opinions
Email marketers generally agree that a DNS outage, even if sending is paused, can potentially impact email deliverability when sending resumes. The primary concerns revolve around DNS propagation delays, sender reputation, and the potential for increased bounces or spam complaints. Gradual resumption of sending, close monitoring of engagement metrics, and checking inbox placement are commonly recommended strategies.
Key opinions
- Monitor Metrics: Key metrics such as bounce rates, open rates, and click-through rates should be closely monitored after resuming sends. Sudden spikes in bounce rates or drops in engagement can indicate deliverability problems.
- Gradual Resumption: Instead of immediately resuming full sending volume, a gradual increase is recommended to re-establish sender reputation with ISPs.
- Inbox Placement: Checking inbox placement using seed lists or deliverability testing tools is crucial to identify whether emails are landing in the inbox, spam folder, or being blocked.
- Potential for Duplicates: Sending systems may queue emails during an outage. Resending emails immediately could lead to duplicates as the queue automatically retries deliveries.
- Reputation Impact: Pausing sends and then resuming with high volume can affect your IP address, which can lower email placement rates and you will need to warm up your IP address again.
Key considerations
- DNS Propagation: Be aware of DNS propagation delays. Resuming sends too soon might hit resolvers that haven't updated, causing temporary delivery failures.
- Sender Reputation: Consider the potential impact on sender reputation. A sudden increase in sending volume after an outage might trigger spam filters.
- Audience Segmentation: Segment your audience and gradually increase send volume to smaller segments first, monitoring performance before sending to your entire list.
- Deliverability Testing: Performing a deliverability test with a tool is crucial after resuming sending to assess potential impact on inbox placement.
- Warm-up strategy: Plan a warm-up strategy to rebuild your sending reputation, if a long pause in sending occurs
Marketer view
Email marketer from SendGrid advises monitoring engagement metrics (opens, clicks) closely after resuming sends. Low engagement can signal deliverability problems and impact future sending reputation.
4 Feb 2022 - SendGrid
Marketer view
Email marketer from Mailchimp suggests gradually increasing sending volume after any interruption. This helps re-establish your sending reputation with ISPs and prevent deliverability issues.
10 Feb 2023 - Mailchimp
What the experts say
5 expert opinions
Experts have differing perspectives on the impact of a DNS outage on email deliverability. Some argue that ESPs' caching mechanisms should mitigate significant issues, while others highlight potential for temporary bounces, delayed deliveries due to TTLs, and indirect effects on sender reputation if complaints or bounces increase during the recovery period. Monitoring bounce logs and feedback loops is consistently recommended.
Key opinions
- Caching Mitigates: ESPs typically run recursive resolvers locally that cache DNS records, minimizing the impact of DNS outages.
- Temporary Spikes: Expect temporary spikes in metrics, but normal delivery logic should handle them.
- TTL Impact: Short TTLs can lead to delayed deliveries if ESPs aren't adhering to them.
- Bounce Potential: DNS record propagation delays can lead to temporary bounces and deferrals.
- Reputation Risk: Increased complaints/bounces during recovery can indirectly impact sender reputation.
Key considerations
- Bounce Monitoring: Closely monitor bounce logs for increased errors post-outage.
- Feedback Loops: Pay attention to feedback loops to detect any increased complaint rates.
- TTL Adherence: ESPs need to adhere to the TTLs of DNS records to ensure timely updates.
- Outage Length: The duration of the outage should be considered.
Expert view
Expert from Email Geeks says that five minute TTLs aren’t uncommon so unless ESPs are hanging on to records longer than they should they’ll see delayed deliveries.
25 Nov 2022 - Email Geeks
Expert view
Expert from Email Geeks expects some metrics to spike temporarily, but nothing normal delivery logic can’t handle.
25 Aug 2023 - Email Geeks
What the documentation says
5 technical articles
Technical documentation indicates that DNS outages can impact email deliverability, even if sends are paused and resumed. DNS propagation delays mean resolvers might not have updated records, leading to temporary failures. While DNS resolvers retry, messages may be delayed. TTLs affect caching duration, and DNSSEC adds complexity, potentially causing validation failures. Root server redundancy minimizes widespread failures, but regional issues can still occur.
Key findings
- Propagation Delays: DNS changes can take up to 48 hours to propagate fully, causing temporary failures upon resumption.
- Retry Mechanisms: DNS resolvers retry failed lookups, potentially delaying but not necessarily dropping messages.
- TTL Impact: Time-To-Live (TTL) values determine how long DNS records are cached, affecting update speed after an outage.
- DNSSEC Complications: DNSSEC can amplify the impact, causing validation failures until records are updated and validated.
- Root Server Redundancy: Root server distribution minimizes widespread failures, but regional issues are possible.
Key considerations
- Wait for Propagation: Allow sufficient time for DNS records to propagate before resuming sends.
- Monitor for Delays: Be prepared for potential message delays due to DNS retry mechanisms.
- Consider TTL Values: Understand how TTL values influence DNS record update speeds.
- Check DNSSEC Validation: If DNSSEC is enabled, verify proper record validation after the outage.
- Regional Impact: Consider potential regional impacts if the outage affected specific geographical areas.
Technical article
Documentation from RFC Editor explains that DNS resolvers implement retry mechanisms to handle temporary failures. Therefore, messages might be delayed, not necessarily dropped, during a brief outage.
6 Apr 2023 - RFC Editor
Technical article
Documentation from AWS Route 53 states that DNS records have a Time-To-Live (TTL), which determines how long resolvers cache the information. Shorter TTLs mean faster updates after an outage.
4 Sep 2024 - AWS Documentation
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