Summary
A comprehensive analysis from experts, marketers, and documentation points to a nuanced approach to retrying emails after receiving a "Connection Error." A prevalent theme suggests that these errors often indicate a hard bounce, a block (potentially an Office 365 tenant block requiring manual intervention), or a broader domain health issue. Consequently, repeatedly sending emails to addresses that generate such errors damages sender reputation and negatively impacts deliverability. While some sources suggest segmenting these errors and potentially retrying after a delay if the error appears transient (as indicated by 4xx SMTP codes or soft bounce classification), the overriding recommendation is to prioritize list cleaning by removing addresses causing consistent connection errors. Analyzing bounce messages to discern the nature of the error (temporary vs. permanent) is crucial in making informed decisions about retries.
Key findings
- Potential Block: Connection errors may signify an outright block, particularly an Office 365 tenant block, that needs direct domain owner intervention.
- Hard Bounce Indication: Many sources treat connection errors as a type of hard bounce, which should not be retried.
- Domain Health Implication: Active blocking or repeated connection errors imply issues with your sending domain's health.
- Reputation Damage Risk: Retrying emails repeatedly after connection errors worsens sender reputation and deliverability.
- Transient vs. Permanent: Some connection errors are transient, but many indicate a more fundamental problem.
- Segmentation Potential: If deemed transient, segmenting these errors and retrying with a delay may be an option.
Key considerations
- Bounce Analysis: Carefully analyze bounce messages to distinguish between temporary and permanent connection issues.
- SMTP Code Examination: Examine SMTP reply codes (4xx vs. 5xx) to understand the transient or permanent nature of the error.
- List Hygiene Priority: Prioritize maintaining a clean email list by removing addresses that cause frequent connection errors.
- Retrial Justification: If retrying, carefully justify the decision based on the nature of the error and potential for successful delivery.
- Manual Intervention: Consider manual investigation if the connection error implies an Office 365 tenant block or similar issue requiring direct engagement.
- Reputation Management: Always weigh the potential benefit of retrying against the risk of damaging sender reputation.
What email marketers say
7 marketer opinions
The consensus among email marketers is generally against retrying emails after receiving a "Connection Error" bounce reason. While some suggest that these errors might be temporary and segmenting them could allow for a later retry, the prevailing view is that such errors often indicate a hard bounce or a block. Repeatedly sending to these addresses damages sender reputation and negatively impacts deliverability. Maintaining a clean email list by removing addresses that generate connection errors is widely recommended as a best practice.
Key opinions
- Domain Health: Active blocking suggests poor domain health, making retries unlikely to succeed.
- Hard Bounce: Connection errors often equate to hard bounces, making retries detrimental to sender reputation.
- List Cleaning: Maintaining a clean email list by removing hard bounces is crucial for deliverability.
- Reputation Damage: Repeatedly sending to addresses causing connection errors damages sender reputation.
- Segmentation: Segmenting connection errors allows for potential retries if the error is temporary.
Key considerations
- Error Type: Determine if the connection error is temporary or permanent before retrying.
- Sender Reputation: Prioritize protecting sender reputation over attempting to deliver to problematic addresses.
- List Hygiene: Implement a robust list cleaning process to remove invalid or problematic addresses.
- Monitoring: Monitor bounce messages to understand reasons for failures and adjust sending strategy accordingly.
Marketer view
Email marketer from Reddit recommends against retrying emails that resulted in a connection error. Suggesting it's more efficient to clean your list to preserve your sender reputation rather than attempting to resend. The poster mentions that they have experience with bulk email and keeping sender reputation intact.
26 Jan 2025 - Reddit
Marketer view
Marketer from Email Geeks explains that the reported "Connection Error" is actually a block. The fact that the emails are being actively blocked indicates that the domain health is already poor.
8 Jan 2025 - Email Geeks
What the experts say
2 expert opinions
Experts generally advise caution when retrying emails after a "Connection Error." One expert identifies that the error may be due to an Office 365 tenant block, requiring direct contact with the domain owner and each tenant for resolution, making retries impractical. Another expert emphasizes analyzing bounce messages to differentiate between temporary and permanent failures. Recurring connection errors from the same domain suggest a more serious issue where retries are unlikely to succeed.
Key opinions
- O365 Block: A connection error may indicate an Office 365 tenant block requiring manual intervention.
- Analyze Bounces: Analyzing bounce messages is crucial to understanding the nature of the connection error.
- Temporary vs. Permanent: Differentiate between temporary and permanent connection errors to determine if a retry is appropriate.
- Recurring Errors: Repeated connection errors from the same domain suggest a more severe issue, making retries futile.
Key considerations
- Intervention Needed: If the error is an O365 block, manual contact with the domain owner and tenants is necessary.
- Monitoring: Implement processes to monitor and analyze connection error bounce messages.
- Retry Appropriateness: Assess the nature of the error to determine if a retry is likely to succeed or if the address should be removed.
- Frequency: If an email address causes connection errors often then avoid retrying as that causes harm to sender reputation.
Expert view
Expert from Word to the Wise explains the importance of analyzing bounce messages to understand the reason for the failure. A connection error can be temporary, so monitoring these responses separately from permanent failures is recommended to determine if a retry is appropriate. However, repeated connection errors from the same domain often indicates a more serious problem and retrying is not likely to succeed.
19 Oct 2023 - Word to the Wise
Expert view
Expert from Email Geeks explains that retrying the email is pointless because it appears to be an Office 365 tenant block. To resolve this, the domain owner (not O365) needs to be contacted to unblock the domain, and each tenant would need to be contacted individually.
12 Nov 2022 - Email Geeks
What the documentation says
4 technical articles
Email documentation suggests a nuanced approach to retrying emails after a "Connection Error" bounce. While Mailjet indicates that such errors can be temporary, warranting a retry after a delay, persistent errors signal a deeper problem. Amazon SES classifies connection errors as hard bounces, advising against repeated retries. RFC Editor distinguishes between 4xx (transient) and 5xx (permanent) SMTP reply codes, advocating for retries for the former and removal for the latter. SparkPost reinforces the transient vs. permanent bounce distinction, recommending retries only for transient bounces.
Key findings
- Temporary vs. Permanent: Connection errors can indicate either a temporary or permanent issue.
- Retry on Transient: Retrying is potentially appropriate for transient failures (4xx codes, soft bounces).
- Avoid on Permanent: Retrying is not recommended for permanent failures (5xx codes, hard bounces).
- Persistent Errors: Persistent connection errors often suggest a more significant underlying problem.
Key considerations
- SMTP Codes: Examine SMTP reply codes to determine the nature of the connection error (4xx vs 5xx).
- Bounce Type: Classify the bounce as transient or permanent.
- Error Persistence: Monitor for persistent connection errors from the same recipient.
- Delay Before Retry: If retrying, implement a delay to allow the recipient server to recover.
Technical article
Documentation from Mailjet explains that a "Connection Error" (or timeout error) often indicates a temporary problem on the recipient's server. Retrying after a delay might be successful, but persistent errors suggest a more significant issue like the recipient server being down or blocking the sender.
13 Dec 2021 - Mailjet
Technical article
Documentation from SparkPost explains the difference between transient and permanent bounces. They elaborate that a transient bounce suggests a retry could be attempted, while a permanent bounce means it should not be retried.
21 Nov 2022 - SparkPost
