SMTP Relay Errors
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SectionsWhat is SMTP Relaying?
What are the symptoms of a relaying error?
How do I whitelist the Desk.com IPs?
The list of server IPs is listed here.
- Emails being bounced back or unable to be sent.
- Emails being stuck in the Desk.com Outbox.
- Customers not receiving their emails
- Similar error message to the ones below appearing in your error logs:
→ 550 5.7.1 Unable to relay for email@example.com\n
→ 554 5.7.1 <firstname.lastname@example.org>: Relay access denied\r\n
→ 511 Host Not Authorized to Relay\r\n
→ 550 relay not permitted\r\n
→ 553 5.3.0 Rejected or Address Rejected
→ 553 5.3.0 Address Rejected
→Unknown or illegal alias
→No such user here
→server does not allow relaying
→553 Relaying disallowed
These errors are the mail server's way of telling Desk.com that it is not configured to allow it's IPs to send emails.
In most environments, whitelisting on the mail server alone is sufficient. However, if you are using any of the following security applications or devices, additional whitelist configuration or exceptions may be required:
- Spam Filter
- Endpoint application
- Front End Relay Server
If you use a hosted spam filtering service, such as Microsoft Exchange Online Protection, Microsoft Forefront Online Protection for Exchange or a similar service, you may need to contact your provider to discuss the errors and determine if any whitelisting needs to be done for the Desk.com IP's.
You should also verify that your sites' SPF records are configured properly. Please go to www.mxtoolbox.com and enter your domain name without the www. ie: yourcompany.com. This should give you your SPF record. Make sure there are no restrictions on what sites/domains can send email in your company.
To test the Desk.com IP addresses against the SPF record, you can use this SPF Policy Tester tool.
Plug in one of the Desk.com IP addresses from the list of allowed IP addresses from earlier in the article. Then plug in your sending email address in the second field. If the tool returns a failure, then the SPF record is incorrectly configured.
It's not always the case, (THIS IS NOT REQUIRED) but if your network administrators do require an SPF record for these IP addresses, we suggest using the SPF Wizard to rebuild your SPF record to include the IP addresses from the article above.
You should consult with your Network Administrators before attempting any SPF record changes in DNS, as doing this improperly can cause serious problems for your email system.
I have whitelisted the IPs and verified that my SPF record is not causing the issue, but am still receiving the relay error, now what?
If you feel that you have applied the whitelist correctly, and continue to receive a relaying error, then you may have missed a device or exception in one of your applications/devices.
If you are still having issues, it is highly recommended that you get your email server administrator or network administrators to sniff out the Desk.com whitelist IPs on your network and locate the failure point. The Desk.com servers will try to send an email every minute or two, and the connection attempts should be easily visible in your network and mail server logs.
Proper whitelisting is required in order for Desk.com to function properly when sending mail. While the Desk.com support team can provide guidance on the potential failure points, the actual configuration is done entirely in your own or your hosting provider's network environment.