5.7.14 bounce: trust relationship required
5.7.14Trust relationship requiredPermanent: retrying will not help
534 5.7.14 Please log in with your web browser and then try again
What it means
RFC 5248 defines X.7.14, “trust relationship required”, with reply 535 or 554. The submission server needs a configured trust relationship with a third-party server to fetch the message content, as in BURL submission (RFC 4468), where the client asks the submission server to pull the message from an IMAP server.
That original meaning is rare. You are much more likely to meet 5.7.14 from Gmail, which uses 534 5.7.14 when it wants the user to sign in through a web browser first, usually after a sign-in from a new location or device looked suspicious. The message did not go out; the client login was refused.
Either way, nothing reached a recipient. The fix happens on the account or between the servers involved, not on the receiving side of the message. There is no 4-class variant in regular use.
Likely causes
- Gmail blocking a client sign-in it considers unusual and asking for interactive confirmation.
- A client using legacy password authentication that Google no longer allows for the account.
- A BURL submission where the submission server has no trust set up with the IMAP server holding the message.
- A mismatch between the IMAP URL the client supplied and the servers the submission server trusts.
How to fix it
- For Gmail, sign in to the account in a browser from the same network and confirm any security prompt.
- Switch the client to OAuth sign-in or use an app password if the account has 2-Step Verification.
- For BURL, configure the submission server to trust the IMAP server (as its documentation describes) or have the client send the message with DATA instead.
- Retry sending after the change and watch for a 235 authentication success.
Checks that apply
- SMTP Diagnostics Shows which authentication mechanisms the submission server offers, including whether OAuth is available.
- What Is My IP Shows the public IP your client uses, which helps explain why a provider considers a sign-in unusual.
FAQ
- Is my Gmail account hacked if I see 5.7.14?
- Not necessarily. Google is asking you to confirm a sign-in it considered unusual. Do check recent security activity in the account to be sure.
- Does 5.7.14 mean the recipient blocked me?
- No. It is about your login to the sending server; the message never reached the recipient.