Summary
Even when Google Postmaster Tools shows no immediate errors, bounces can still occur due to a multitude of factors often outside the direct visibility of Postmaster Tools. These include routing problems, potential placement on a 'death penalty routing list', high load on the ESP's sending MTAs, the inherent limitations of Postmaster Tools providing only Google's perspective and statistical sampling, transient errors not immediately reflected, non-robust sending infrastructure, SMTP timeout errors, DMARC policies and authentication failures, issues related to rogue IPs within shared blocks, sub-optimal content, delays in Postmaster Tools reporting, IPs temporarily blacklisted on smaller lists, spam traps, poor list hygiene, compromised accounts, and external issues with recipient mail servers or intermediate hops.
Key findings
- Routing Issues: Routing problems outside of your control can cause bounces.
- Death Penalty Routing: IPs may be on a 'death penalty routing list' which limits deliverability.
- Transient Errors: Transient errors like timeouts may not be immediately reflected.
- ESP MTA Load: High load on ESP's MTAs causes delays and connection issues.
- Limited Google View: Postmaster Tools provides only Google's view, missing external factors.
- Rogue IPs: One bad IP in a shared block can affect deliverability.
- Content Matters: Sub-optimal content triggers spam filters, causing bounces.
- Reporting Delays: Postmaster Tools data is delayed, not real-time.
- Smaller Blacklists: IPs can be blacklisted on smaller lists not monitored by Google.
- Spam Traps: Hitting spam traps damages sender reputation, increases bounces.
- Poor List Hygiene: Invalid/inactive addresses increase bounces.
- Compromised Account: A compromised account can increase bounce rates.
- External Issues: Recipient mail server issues lead to bounces.
- Sampling: Google Postmaster Tools uses sampling and does not see all emails.
Key considerations
- Check Routing: Investigate potential routing issues.
- Monitor ESP Load: Ensure ESP's MTAs aren't overloaded.
- External Blacklists: Check for listing on external blacklists.
- Content Optimization: Review and optimize email content for deliverability.
- Authentication: Verify proper setup of SPF, DKIM, DMARC.
- List Hygiene: Regularly clean and verify email lists.
- Security: Ensure good security, check for strange events such as sudden increase in bounces
- Broaden Monitoring: Use multiple tools, not just Postmaster Tools.
- Interpret Delays: Remember data delays within Postmaster Tools.
- Sampling: Remember that Google Postmaster tools reports via sampling, it is not a complete overview.
What email marketers say
11 marketer opinions
Even when Google Postmaster Tools indicates no errors, bounces can still occur due to various factors. These include temporary network issues, rogue IPs, content triggering spam filters, problems with sender authentication (SPF, DKIM, DMARC), delays in Postmaster Tools reporting, temporary blacklisting on smaller blocklists, hitting spam traps, poor list hygiene, compromised accounts, and general delays in displayed metrics. The tool also doesn't take into account other email provider blacklists.
Key opinions
- Networking Issues: Temporary networking problems, not related to reputation, can cause bounces.
- Rogue IPs: A single problematic IP address within a block can negatively affect deliverability.
- Content Matters: Even with a good reputation, spammy content can lead to bounces.
- Reporting Delays: Google Postmaster Tools data isn't real-time; delays can mask current issues.
- Authentication is Critical: Authentication issues not immediately flagged can still cause bounces.
- Smaller Blacklists: Temporary listings on smaller blocklists may not be monitored by Google but can still cause bounces.
- Spam Traps: Hitting spam traps severely damages sender reputation and increases bounces, often before being reflected in Postmaster Tools.
- List Hygiene: Poor list hygiene is a major cause of bounces, regardless of reputation.
- Compromised Accounts: A sudden increase in bounces may be caused by a compromised account
- Statistical sampling: Postmaster tools is based on statistical sampling, it does not see all emails.
Key considerations
- Monitor Extensively: Don't rely solely on Google Postmaster Tools; use multiple monitoring tools.
- Check Blacklists: Use external blacklist checkers to verify IP and domain status.
- Review Content: Regularly audit email content for spam trigger words and poor formatting.
- Verify Authentication: Double-check SPF, DKIM, and DMARC configurations for accuracy.
- Clean Lists Regularly: Implement a robust list hygiene process to remove invalid or inactive addresses.
- Check Account Security: Ensure account security, look for sudden bounce rates as a sign of something gone wrong
Marketer view
Marketer from Email Geeks shares an experience where a customer seemed to be on a good sender block, except one IP address in the block caused variance, possibly due to a 'rogue IP' from a bad block wandering into the wrong neighborhood.
13 May 2023 - Email Geeks
Marketer view
Email marketer from SendGrid explains that there can be delays in Google Postmaster Tools reporting, so recent sending activity might not immediately reflect. It's important to look at trends over time and compare the data with other monitoring tools to get a clearer picture.
12 Mar 2023 - SendGrid
What the experts say
5 expert opinions
Google Postmaster Tools showing no errors, but bounces occurring can be due to several factors outside the direct view of Postmaster Tools. These include routing problems, potential placement on a 'death penalty routing list', high load on the ESP's sending MTAs, the inherent limitations of Postmaster Tools providing only Google's perspective, issues with recipient mail servers or intermediate hops, the tool's reliance on statistical sampling, and significant data delays within Postmaster Tools.
Key opinions
- Routing Problems: The bounces may be caused by a routing issue outside of the control of your mail server.
- Death Penalty List: Your IP address may be on a routing list that severely limits its ability to be delivered.
- ESP MTA Load: High load on the ESP's MTAs can cause delays and connection issues, leading to bounces.
- Limited Perspective: Postmaster Tools only reflects Google's view and doesn't capture issues with other mail systems.
- External Issues: Bounces may be due to problems with recipient mail servers or intermediate hops outside your control.
- Statistical Sampling: The tools are based on statistical sampling, it does not see all emails.
- Data Delays: Information in Postmaster Tools is not real-time, causing discrepancies between current bounces and reported data.
Key considerations
- Investigate Routing: Check for any known routing issues affecting your sending infrastructure.
- Monitor MTA Load: Ensure your ESP's MTAs are not overloaded, which could be causing delays.
- Broaden Monitoring: Use additional monitoring tools to gain a more complete picture of deliverability.
- Factor in Delays: Be aware that Postmaster Tools data is delayed and might not reflect immediate bounce issues.
- Sampling: Remember that Postmaster tools does not see all emails - it takes samples of the data to show you in the interface.
Expert view
Expert from Word to the Wise (referring to Laura Atkins' expertise) explains that the information displayed in Google Postmaster Tools is not real-time. There can be significant delays (hours or even days) in the data being reflected. Therefore, bounces happening now may not be visible immediately in the dashboards.
11 Aug 2023 - Word to the Wise
Expert view
Expert from Email Geeks suggests the issue could be a routing problem.
27 Nov 2022 - Email Geeks
What the documentation says
3 technical articles
Even if Google Postmaster Tools shows no immediate errors, bounces can still occur due to temporary or transient issues like timeouts and network problems that might not be immediately reflected. These are often caused by a non-robust email infrastructure that cannot compensate for small sporadic issues. Furthermore, issues with DMARC policies (set to reject) and intermittent authentication failures can cause bounces that Postmaster Tools might not report immediately due to sampling rates.
Key findings
- Transient Errors: Temporary errors like timeouts and network issues may not be immediately reflected in Postmaster Tools.
- Non-Robust Infrastructure: A non-robust sending infrastructure can exacerbate the impact of transient errors, leading to bounces.
- SMTP Timeouts: SMTP timeout errors cause bounces but may not be instantly visible in Postmaster Tools logs.
- DMARC Reject Policy: DMARC policies set to reject, combined with sporadic authentication failures, result in bounces not immediately reported by Google.
- Sampling Rates: Reporting is based on statistical sampling, it does not see all emails and will not report every bounced email.
Key considerations
- Infrastructure Stability: Ensure a robust email sending infrastructure to handle transient errors effectively.
- Monitor Logs: Regularly monitor SMTP logs to identify timeout issues.
- Audit DMARC: Review and audit DMARC policies and authentication methods for consistency.
- Sampling Rates: Postmaster tools reports data based on a statistical sample. It does not show all data.
Technical article
Documentation from DMARC.org explains that if a DMARC policy is set to reject, but the authentication checks are failing sporadically or for certain mail streams, this will result in bounces. However, google postmaster tools may not report the individual issues immediately depending on sampling rates
29 Sep 2022 - DMARC.org
Technical article
Documentation from Google Developers explains that 'Transient' or temporary errors (like timeouts or network issues) might not be reflected immediately in Postmaster Tools, especially if they are infrequent. These can still result in bounces, especially if your sending infrastructure isn't robust enough to handle them.
25 Dec 2022 - Google Developers
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