550 5.1.1 The email account that you tried to reach does not exist
There is no mailbox at that address on Gmail or on the Workspace domain. Nothing about your sending setup is wrong; the recipient address is. Gmail checks this at RCPT TO, so the bounce usually comes back within seconds.
What the server replies
550-5.1.1 The email account that you tried to reach does not exist. Please try 550-5.1.1 double-checking the recipient's email address for typos or 550-5.1.1 unnecessary spaces. For more information, go to 550 5.1.1 https://support.google.com/mail/?p=NoSuchUser
- Sent by
- Gmail
- Type
- PermanentRetry fails
- About
- Recipient problems
- Enhanced code
- 5.1.1
Who sends it
Gmail and Google Workspace inbound servers at RCPT TO, for any address that does not match a user, group or alias. Workspace domains that use a catch-all do not produce it.
Why it happens
- A typo in the local part, or a trailing space or dot that a form let through.
- The person left the company and Workspace deleted or suspended the account.
- An old address on a purchased or scraped list that never existed in the first place.
- Case or punctuation differences that matter on some systems but not on Gmail, which can mislead you into "fixing" a working address.
How to fix it
Verify the address
Ask the recipient for the address in writing or check a recent message from them. Gmail ignores dots and anything after a plus sign, so those are not the cause.
Suppress it
Add the address to your suppression list after one hard bounce. Repeatedly sending to unknown users is one of the strongest spam signals Gmail uses against a sender.
Audit the list
If more than two percent of a send hits this code, the list is stale. Run it through a verification service before the next send and remove anything older than a year with no engagement.
Check it yourself
These free tools show the records and connections behind this code for your own domain or server.
Related codes
- 550 5.1.1 User unknown / recipient address rejectedThe most common bounce there is: the mailbox does not exist.
- 550 5.4.1 Recipient address rejected: Access deniedExchange Online looked the recipient up in the tenant's directory and did not find it, so it refused the address at RCPT TO.
- 550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookupExchange tried to resolve the recipient address against its directory and found nothing.
- 554 delivery error: dd This user doesn't have a yahoo.com accountThe recipient address does not exist at Yahoo.
Sources
Fewer bounces to look up.
Faivelo sends from authenticated, warmed infrastructure, turns permanent bounces into one clean event for your application and keeps the address out of future sends.
Free tier included. No card needed.
Other free tools
All tools- Email DNS checkerCheck MX, SPF, DKIM, DMARC and reverse DNS for any domain and get the exact records to add or fix.
- DMARC checkerLook up a domain's DMARC record, read every tag in plain words and see what to tighten next.
- DMARC record generatorBuild a valid DMARC record from a few choices and copy the host and value into your DNS.
- DMARC report analyzerDrop in a DMARC aggregate report and see who is sending as your domain and whether they pass.
- SMTP connection testerConnect to any SMTP server, check TLS and the login step, and see each stage with its timing.
- Email header analyzerPaste raw headers to see every hop, where the delay was, and whether SPF, DKIM and DMARC passed.
- Email address validatorCheck whether an address is well formed, whether its domain accepts mail, and whether it is disposable or a role account.