Why would I receive mail back as undeliverable?

Not every address is 100% validated. Although we are running through a multi-step verification process there are times that the USPS system won't validate it even if it seems to match. So if you are mailing on your own - you may be mailing to unvalidated addresses. If you are mailing through our services, we scrub all lists prior to mailing to ensure we are only sending to validated addresses. That being said, even if an address is USPS CASS Certified, it may still come back as undeliverable, as there are still factors out of our control here.  

Some reasons a letter make come back as undeliverable include, but are not limited to: 

• Vacant Address - the address exists, but the post office has it marked as a vacant address 
• No Mail Receptable - there isn't an accessible mail drop 
• Delivery not Active or suspended - address is valid, but is marked as inactive or suspended at the post office 
• Undeliverable as addressed - the name on the envelope doesn't match who the post office has on file for this address 
• May be missing a unit number - an address will still validate, but may be missing the secondary component for deliverability 
• Inaccessible - mail delivery driver was unable to access the location 

Some of these are at the discretion of the mail delivery driver which is an unpredictable human element in this process. 

Updated on: 23/07/2025