Alibaba Mail:How to Handle Email Delivery Failure

When an email fails to deliver, Alibaba Mail sends a bounce message that identifies the cause and guides you to a fix.

When an email fails to deliver, you receive a bounce message containing the reason for the failure. Before troubleshooting, determine whether the failure is permanent or temporary — this tells you whether to act immediately or wait for a retry.

• Hard bounce (permanent failure): The email cannot be delivered. Common causes include an invalid recipient address, a non-existent domain, or a policy-based rejection. Fix the underlying issue before resending.

• Soft bounce (temporary failure): The email was deferred due to a transient condition, such as a full mailbox or a temporarily unavailable server. The mail server typically retries automatically.

Step 1: Read the bounce message

Read the bounce message to identify the failure type.

• Check the Reason field for a plain-language explanation of why the email was rejected.

• If the explanation is unclear, check the Reply field for the raw Simple Mail Transfer Protocol (SMTP) response from the recipient's server.

Use the SMTP response code to classify the failure:

Step 2: Check DNS settings

Verify that your domain's Domain Name System (DNS) records are correctly configured.

What to verify:

• MX record: Confirm the MX record for your domain is valid and points to the correct mail server.

• SPF: Confirm your sending IP address is authorized in your SPF record.

• DKIM: Confirm your outgoing messages are cryptographically signed.

• DMARC: Confirm a DMARC policy exists and aligns with your SPF and DKIM results.

Use Alibaba Cloud DNS to query DNS records.

As of February 2024, Gmail and Yahoo require full SPF, DKIM, and DMARC authentication for all inbound mail. Emails sent to gmail.com, googleemail.com, yahoo.com, aol.com, and other Google or Yahoo domains without all three protocols configured may bounce or land in the spam folder. If you send to these providers, configure SPF, DKIM, and DMARC for your sending domain. Contact the Alibaba Mail team for configuration assistance. See Google's sender guidelines for details.

Step 3: Check the recipient address

Verify the recipient address is valid.

• Check for typos, extra spaces, or incorrect domain names.

• Confirm the recipient's account is active and has not exceeded its storage quota.

Step 4: Check attachment size

If the email has an attachment, confirm the file size does not exceed the recipient mailbox's limit. Reduce the attachment size or share the file through a file-sharing service if needed.

Step 5: Check email content

Spam filters evaluate message content in addition to sender infrastructure. Check for the following:

• Misleading or overly promotional subject lines

• Content or links commonly associated with spam

• URL shorteners or suspicious redirect links

• A missing plain-text version of the email

Remove any content that could trigger spam filters.

Step 6: Check the sender address

Confirm the sender account is in good standing.

• Verify the sender address is not flagged as a spam source.

• Check whether the sender's IP address or domain is on a blocklist.

Step 7: Review sending limits

Sending a high volume of email in a short period can trigger anti-spam protection, causing messages to be deferred or blocked.

For bulk or system emails, use Direct Mail instead of Alibaba Mail to avoid affecting delivery for other Alibaba Mail users.

Related documentation: What Is the Direct Mail?

Step 8: Contact the recipient

If the issue persists, contact the recipient through another channel — such as phone, text message, or a messaging app — to confirm their email address and inform them of the delivery problem.

Step 9: Retry sending

After resolving the issue, resend the email.