Summary
A 'tempfail' in Gmail signifies a temporary email delivery failure. It can be triggered by various factors: Gmail suspecting spam (due to content, audience, or sending profile), temporary server issues (overload, downtime), full recipient mailboxes, email authentication problems (SPF, DKIM, DMARC), low sender reputation leading to throttling, missing reverse DNS (rDNS) records, IP address issues (blocklisting, lacking warm-up), excessively large messages, or Gmail's use of greylisting for unknown senders. These failures are generally transient, and mail servers will typically retry delivery. The frequency (e.g., 0.1%) should be monitored, comparing delivery and open rates across ISPs.
Key findings
- Spam Suspicion: Gmail's spam filters are a significant cause of tempfails. Content, audience targeting, and list hygiene are crucial.
- Server Issues: Temporary server problems (both sender and receiver) can impede delivery.
- Authentication Failures: Incorrect or missing email authentication records (SPF, DKIM, DMARC) trigger temporary rejections.
- Reputation Matters: A low sender reputation leads to throttling and temporary blocks.
- DNS Configuration: Missing or misconfigured reverse DNS records hinder server verification.
- IP Address Health: IP address reputation (blocklisting, warm-up) influences deliverability.
- Greylisting: Gmail may use greylisting as an initial spam check, causing an initial tempfail.
- Message Size Limits: Exceeding message size limits results in temporary failures.
- SMTP Codes: Tempfails often correspond to temporary SMTP errors (4xx codes).
Key considerations
- Monitor Stats: Track delivery stats across different ISPs to identify issues specific to Gmail.
- Review Content: Analyze email content for potential spam triggers.
- Maintain Lists: Practice good list hygiene to ensure engaged recipients.
- Authenticate Emails: Implement and verify SPF, DKIM, and DMARC records.
- Manage Reputation: Actively monitor and improve sender reputation.
- Verify DNS: Ensure correct reverse DNS configuration.
- Monitor Blocklists: Regularly check IP addresses against blocklists.
- Warm-up IPs: Properly warm up new IP addresses before sending large volumes.
- Retry Configuration: Confirm sending server automatically retries deliveries after a tempfail.
- Volume Management: Implement sender throttling to manage email volume
What email marketers say
11 marketer opinions
A 'tempfail' in Gmail indicates a temporary delivery issue. This can stem from various reasons, including the email being suspected as spam, temporary server problems, full mailboxes, email authentication issues (SPF, DKIM, DMARC), low sender reputation, missing reverse DNS records, or IP address related issues (blocklisting, insufficient warm-up). Temporary SMTP errors (4xx codes) signal the server's inability to process the request temporarily, potentially due to resource limitations. Gmail may also employ greylisting or throttling for unknown senders, causing tempfails.
Key opinions
- Spam Detection: Gmail may classify emails as suspected spam, causing temporary blocks. Review email content, audience, and list hygiene.
- Server Issues: Temporary server problems, such as downtime or overload, can result in tempfails.
- Authentication: Incorrect or missing SPF, DKIM, or DMARC records can lead to Gmail temporarily rejecting emails.
- Sender Reputation: A low sender reputation can trigger throttling or temporary blocks by Gmail.
- Reverse DNS: Missing or incorrect reverse DNS records can cause temporary failures as Gmail verifies the sending server's legitimacy.
- IP Address: IP address issues, like being on a blocklist or lacking a warm-up period, can result in tempfails.
- Greylisting: Gmail (and other providers) might use greylisting, causing an initial temporary failure as they verify the sender.
- SMTP Errors: Temporary SMTP errors (4xx codes) indicate the server is temporarily unable to process the request, often due to resource limitations.
Key considerations
- Delivery Stats: Monitor delivery stats across different ISPs to identify potential deliverability issues.
- Open Rates: Compare Gmail open rates with other ISPs to detect if Gmail is filtering emails to junk.
- Email Content: Analyze email content for potential spam triggers.
- List Hygiene: Maintain good list acquisition and hygiene practices to ensure recipients have requested the emails.
- Authentication Records: Verify and configure SPF, DKIM, and DMARC records to authenticate emails.
- Sender Reputation: Monitor and improve sender reputation to avoid throttling or blocks.
- Reverse DNS: Ensure the sending server has a valid reverse DNS record.
- Blocklist Monitoring: Monitor IP addresses for inclusion on blocklists and take action to be removed if listed.
- IP Warm-up: For new IP addresses, follow a proper warm-up procedure to establish a positive sending reputation.
Marketer view
Email marketer from Email on Acid explains that a soft bounce, potentially indicated by a tempfail, can be triggered by factors like a full mailbox, a server being down, or the email content triggering spam filters. They recommend reviewing your sender reputation and email content.
31 Dec 2024 - Email on Acid
Marketer view
Email marketer from SendPulse shares that a temporary failure can occur due to IP address related issues, for example being on a blocklist, or the IP not having enough of a 'warm-up' period.
17 Jun 2022 - SendPulse
What the experts say
2 expert opinions
Tempfails in Gmail are often caused by greylisting or throttling mechanisms. Greylisting involves the receiving server (Gmail) temporarily rejecting emails from unknown senders to verify their legitimacy. Legitimate servers retry sending, while spammers typically do not. Throttling is a similar process used to manage the volume of emails from a particular sender, reducing the likelihood of spam.
Key opinions
- Greylisting: Gmail may use greylisting to initially reject emails from unfamiliar senders as a spam prevention technique.
- Throttling: Gmail may use throttling to manage email volumes from senders, preventing overwhelming the system with potential spam.
Key considerations
- Retry Attempts: Ensure your sending server is configured to retry sending emails that initially result in tempfails due to greylisting.
- Volume Management: Implement strategies to manage email sending volumes to avoid triggering throttling mechanisms.
- Sender Reputation: Build and maintain a positive sender reputation to reduce the likelihood of being subjected to greylisting or throttling.
Expert view
Expert from Word to the Wise responds that a common cause of tempfails is greylisting, where the receiving server temporarily rejects an email from an unknown sender to verify its legitimacy. Legitimate servers will retry sending the email.
16 Dec 2021 - Word to the Wise
Expert view
Expert from Spam Resource explains that Gmail may use greylisting or throttling, causing temporary failures. This involves temporarily rejecting emails from unknown senders to combat spam.
22 Mar 2025 - Spam Resource
What the documentation says
4 technical articles
A 'tempfail' in email delivery, as defined in documentation from Google, Mailjet, RFC specifications, and Microsoft, indicates a temporary inability to deliver a message. This can occur due to a range of transient issues at the receiving end, such as a full mailbox, server overload, connection problems, temporary unavailability of the recipient server, or the message being too large. Mail servers typically retry delivery for such messages over a set period.
Key findings
- Temporary Issue: Tempfail signifies a transient issue, suggesting the message might be delivered successfully later.
- Receiver-Side Problems: Causes often reside on the receiving end, such as Gmail's server or the recipient's mailbox.
- Common Causes: Full mailboxes, server overload, connection problems, and unavailable resources are common reasons.
- Message Size: An excessively large email can also trigger a temporary failure.
- Retry Mechanism: Mail servers are designed to automatically retry sending messages that initially result in tempfails.
Key considerations
- Message Size Limits: Ensure emails do not exceed size limits imposed by receiving servers to avoid tempfails.
- Server Stability: Monitor the sending server's stability and resource availability to minimize connection problems or overload.
- Automatic Retries: Verify that the sending server is properly configured to automatically retry sending emails that initially encounter tempfails.
- Recipient Mailbox: While you can't control recipient mailboxes, consider that full mailboxes can cause delivery issues.
Technical article
Documentation from Microsoft Support provides insight into delayed and bounced emails. It suggests a possible cause of temporary failure is that the message is too large.
18 Feb 2023 - Microsoft Support
Technical article
Documentation from Mailjet explains that a temporary failure (tempfail) signifies that the message could not be delivered due to a transient issue. Mail servers will typically retry delivery for these messages over a certain period.
13 Jun 2021 - Mailjet
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