Why did I receive the error "Sender Verify Failed" (or some variation thereof)?

Overview

This error (also called Sender Address Verification) occurs when the recipient server performs an MX lookup on the envelope.mail-from address and then fails to locate the MX records for the sending domain. 

You might see this manifest in a few different ways; here are a few of the most common variations:

• 550 Verification failed for <bounce+c72392.3559d@yoursendingdomain.com>\nUnrouteable address\nSender verify failed
• Domain of sender address bounce+c72392.3559d@yoursendingdomain.com does not exist
• 550 550 Verification failed for <bounce+c72392.3559d@yoursendingdomain.com>
• Unrouteable address Sender verify failed
• Sender address rejected: User unknown in virtual mailbox table
• 452 4.5.2 Could not resolve sender domain
• 450 4.1.8 Sender address rejected: Domain not found
• 505 Your domain has no DNS/MX entries
• 550 550 Requested action not taken: mailbox unavailable invalid DNS MX or A/AAAA resource record
• 550 5.2.0 <bounce+c1b91d.4ce06-example=domain.tld@mg.domain.tld> From: Domain is invalid. Please provide a valid From: IB506 <http://x.co/srbounce>
• 550 550 5.7.1 Sender ID (PRA) Domain Does Not Exist

Now that we've seen the errors, we'll explore how to resolve this issue based on your current email sending domain.

Seeing this issue with a subdomain

When configuring any subdomain, while we don't require MX records to be used, as long as you don't already have incoming mail configured for the domain, we highly recommend pointing your MX records for the domain to Mailgun. Why? Doing so serves to proactively correct the Sender Verification Error issue before it begins - always good to be ahead of the curve!

As noted above, some pesky email servers check the subdomain in the envelope.mail-from field for MX records. If those records aren't found, then you're hit with a Sender Verification Error. All is not lost, however - the fix is quite simple; just set the MX records for the subdomain!

Once this is completed, the MX lookups of those email servers should be successful and the servers should accept your messages.

The two MX records that will need to be added to your subdomain are:

When adding your Hostname, you will use the subdomain you have added in AllClients. For example, it might look like send if your domain is set like this in your account: send.allclients.com.

Once the records have been added, you may need to wait the 24-48 hours for them to fully propagate; following this, the error should disappear.

If for any reason you're still seeing that same error, please reach out to our support team and we will help you get this resolved.