550 Mailbox unavailable (permanent)

Gmail

• 550 5.1.1The email account that you tried to reach does not exist. Please double-check the recipient's email address for typos or unnecessary spaces.

  The recipient's address does not exist. Check for typos and stray spaces.

• 550 5.2.1The email account that you tried to reach is inactive.

  The recipient's account is inactive and does not accept mail.

• 550 5.2.1The user you are trying to contact is receiving email at a rate that prevents additional messages from being delivered.

  The recipient is getting mail at a rate that prevents delivery, and the message was rejected. Send it again later.

• 550 5.4.5Daily user sending limit exceeded.

  The sending account reached Gmail's daily sending limit.

• 550 5.4.5Daily SMTP relay limit exceeded for user.

  The daily limit of Google Workspace's SMTP relay service was reached for this user or for the organisation.

• 550 5.5.3Too many recipients for this sender.

  The message has too many recipients for Gmail's limits; split the sending.

• 550 5.7.0Email relay denied ip-address. Invalid credentials for relay for one of the domains in: domain-name (as obtained from HELO and (E)MAIL FROM). Email is being sent from a domain or IP address which isn't registered in your Workspace account. Please login to your Workspace account and verify that your sending device IP address has been registered within the Workspace SMTP Relay Settings.

  Google Workspace's SMTP relay did not recognise the sender: the IP address or the HELO and MAIL FROM domains do not match the relay's configuration.

• 550 5.7.0Email relay denied ip-address. The sending email account has been temporarily suspended due to abuse.

  The account sending through the SMTP relay was temporarily suspended for abuse.

• 550 5.7.0Email sending denied.

  Sending was denied by Google Workspace's SMTP relay service.

• 550 5.7.1The user or domain that you are sending to (or from) has a policy that prohibits the email that you sent. Contact your domain administrator for assistance.

  A rule set by the administrator of the recipient's (or the sender's) domain prohibits the message. Only the administrator can change it.

• 550 5.7.1Invalid credentials for relay ip-address. The IP address you've registered in your Workspace SMTP Relay service doesn't match the domain of the account this email is being sent from. If you are trying to relay email from a domain that isn't registered under your Workspace account or has empty envelope-from:, you must configure your email server either to use SMTP AUTH to identify the sending domain or to present one of your domain names in the HELO or EHLO command.

  Google Workspace's SMTP relay did not recognise the sender: the IP address or the HELO and MAIL FROM domains do not match the relay's configuration.

• 550 5.7.1This message is likely unsolicited email. To reduce the amount of spam sent to Gmail, this message has been blocked.

  Gmail considered the message likely unsolicited and blocked it. Check with Mail delivery test.

• 550 5.7.1This message does not meet IPv6 sending guidelines regarding PTR records and authentication.

  The message sent over IPv6 does not meet Gmail's IPv6 requirements on PTR records and authentication. Check with Mail delivery test.

• 550 5.7.1This message is likely suspicious due to the very low reputation of the sending IP address. To best protect our users from spam, the message has been blocked.

  The sending IP address has a very low reputation at Gmail, so its mail is limited or blocked. Check blocklists, authentication and what you send; Postmaster Tools shows the reputation. Check with Blacklist check.

• 550 5.7.1This message is likely suspicious due to the very low reputation of the sending domain. To best protect our users from spam, the message has been blocked.

  The sending domain has a very low reputation at Gmail, and the message was blocked. Check with Blacklist check.

• 550 5.7.1Messages missing a valid address in the From: header, or having no From: header, are not accepted.

  The message has no From field, or the address in it is not valid. Check with Header analyzer.

• 550 5.7.1Messages missing a valid Message-ID: header are not accepted.

  The message has no valid Message-ID field, which Gmail requires. Check with Header analyzer.

• 550 5.7.1Messages with multiple addresses in the From: header are not accepted.

  The From field holds several addresses, which Gmail does not accept. Check with Header analyzer.

• 550 5.7.1The message contains a unicode character in a disallowed header.

  A header field holds Unicode characters where Gmail does not allow them. Check with Header analyzer.

• 550 5.7.1This message is not RFC 5322 compliant because it has duplicate headers. To reduce the amount of spam sent to Gmail, this message has been blocked.

  The message repeats header fields that must appear only once, so it does not follow RFC 5322. Check with Header analyzer.

• 550 5.7.1This message is not RFC 5322 compliant because the From: header is missing. To reduce the amount of spam sent to Gmail, this message has been blocked.

  The message has no From field, or the address in it is not valid. Check with Header analyzer.

• 550 5.7.1This message is not RFC 5322 compliant because it has multiple From: headers. To reduce the amount of spam sent to Gmail, this message has been blocked.

  The message has more than one From field; RFC 5322 allows only one. Check with Header analyzer.

• 550 5.7.1This message is not RFC 5322 compliant because the From: header has a non-compliant domain name. To reduce the amount of spam sent to Gmail, this message has been blocked.

  The domain in the From address is not a valid domain name. Check with Header analyzer.

• 550 5.7.1This email has been rate limited.

  The message was refused because of Gmail's sending and receiving limits.

• 550 5.7.1The IP you're using to send email is not authorized to send email directly to our servers. Use the SMTP relay at your service provider instead.

  The IP address is not allowed to send directly to Gmail's servers; send through your provider's SMTP server.

• 550 5.7.1Daily SMTP relay sending limit exceeded for this customer.

  The daily limit of Google Workspace's SMTP relay service was reached for this user or for the organisation.

• 550 5.7.1Encoded-word syntax is not permitted in message header header-name. To reduce the amount of spam sent to Gmail, this message has been blocked.

  A header field uses encoded-word syntax (=?…?=) where Gmail does not allow it. Check with Header analyzer.

• 550 5.7.1This message is not RFC 5322 compliant. There are multiple header-name headers. To reduce the amount of spam sent to Gmail, this message has been blocked.

  The message repeats header fields that must appear only once, so it does not follow RFC 5322. Check with Header analyzer.

• 550 5.7.1This message is not RFC 5322 compliant. There is a malformed header- name header. To reduce the amount of spam sent to Gmail, this message has been blocked.

  A header field is malformed. Check with Header analyzer.

• 550 5.7.24The SPF record of the sending domain has one or more suspicious entries.

  Gmail finds one or more entries of the sending domain's SPF suspicious, so it limits or blocks the mail. Review every mechanism in the SPF record. Check with SPF generator.

• 550 5.7.25This message was blocked because the sending IP address doesn't have a PTR record, or the forwarding DNS entry doesn't reference the sending IP address. Gmail requires that sending IP addresses have a PTR record.

  The sending IP address has no PTR, or the PTR name does not lead back to the same address, so Gmail limits or blocks its mail. The PTR is set by whoever holds the IP address. Check with SMTP server check.

• 550 5.7.26This email has been blocked because the sender is unauthenticated. Gmail requires all senders to authenticate with either SPF or DKIM. Authentication results: DKIM = did not pass SPF [domain-name] with ip: [ip-address] = did not pass.

  The message passes neither SPF nor DKIM, and Gmail requires at least one of them from every sender. Check with Mail delivery test.

• 550 5.7.26The (E)MAIL FROM domain [domain-name] has an SPF record with a hard fail policy (-all) but it fails to pass SPF checks with the ip: [ip-address]. To best protect our users from spam and phishing, the message has been blocked.

  The MAIL FROM domain has an SPF record ending in -all, and the sending IP address is not authorised in it. Add the server to SPF or send through an authorised one. Check with SPF generator.

• 550 5.7.26Unauthenticated email from domain-name is not accepted due to domain's DMARC policy. Contact the administrator of domain-name domain if this was legitimate email.

  The message fails DMARC, and the From domain's policy asks for rejection. Legitimate mail must pass SPF or DKIM aligned with From. Check with Mail delivery test.

• 550 5.7.27This message was blocked because it didn't pass SPF authentication. Gmail requires bulk email senders to authenticate their email with SPF.

  The message does not pass SPF, which Gmail requires from bulk senders. Check with SPF generator.

• 550 5.7.28There is an unusual rate of unsolicited email originating from your IP address. To protect our users from spam, email sent from your IP address has been blocked.

  Gmail noticed an unusual rate of unsolicited mail (from the IP address, the netblock, the DKIM or SPF domain, or with a given domain in links) and limits it. Slow down and make sure the recipients asked for the mail. Check with Blacklist check.

• 550 5.7.29This message was blocked because it wasn't sent over a TLS connection. Gmail requires all bulk email senders to use TLS/SSL for SMTP connections.

  The message did not come over a TLS connection, which Gmail requires from bulk senders. Check with Mail delivery test.

• 550 5.7.30This message was blocked because it didn't pass DKIM authentication. Gmail requires bulk email senders to authenticate their email with DKIM.

  The message does not pass DKIM, which Gmail requires from bulk senders. Check with DKIM generator.

• 550 5.7.40Your message was blocked because the sending domain doesn't have a DMARC record or the DMARC record doesn't specify a DMARC policy. Gmail requires all bulk email senders to add a DMARC record to their sending domain.

  The sending domain has no DMARC record, or it has no policy (p=); Gmail requires one from bulk senders. Check with DMARC generator.

Microsoft 365 / Exchange Online

• 550 5.1.20Multiple From addresses are not allowed without Sender address

  The From field holds several addresses but there is no Sender field, which RFC 5322 §3.6.2 requires in that case. Check with Header analyzer.

• 550 5.1.241The message can't be delivered because the recipient is an HVE account. HVE accounts do not have associated mailboxes and can only send messages.

  The recipient is an HVE account, which only sends and does not receive mail.

• 550 5.2.240The email account is not set up properly for the HVE service. Contact your administrator.

  The account or organisation is not set up for, or not allowed to use, the HVE service; the administrator has to fix it.

• 550 5.2.241The HVE account is not properly set up for billing. Contact your administrator.

  The account or organisation is not set up for, or not allowed to use, the HVE service; the administrator has to fix it.

• 550 5.6.240One of MIME Headers is not allowed.

  The message contains a MIME header that is not allowed.

• 550 5.6.241Mandatory From Header is missing or invalid.

  The message has no valid From address (RFC 5322 §3.6.2). Check with Header analyzer.

• 550 5.7.240The application is not allowed for use with an HVE account. Contact your administrator.

  The account or organisation is not set up for, or not allowed to use, the HVE service; the administrator has to fix it.

• 550 5.7.241Trial tenant is not able to use HVE. Contact your administrator.

  The account or organisation is not set up for, or not allowed to use, the HVE service; the administrator has to fix it.

• 550 5.7.242Inactive tenant is not able to use HVE. Contact your administrator.

  The account or organisation is not set up for, or not allowed to use, the HVE service; the administrator has to fix it.

• 550 5.7.243This tenant is blocked from using HVE. Contact your administrator.

  The account or organisation is not set up for, or not allowed to use, the HVE service; the administrator has to fix it.

• 550 5.7.244Message rejected. External sending is not supported for HVE accounts. This message cannot be delivered to external recipients. Please remove any external recipients and try sending again.

  HVE accounts cannot send to recipients outside the organisation.

• 550 5.7.245External sending is not supported for HVE accounts. The message can't be delivered to this recipient.

  HVE accounts cannot send to recipients outside the organisation.

• 550 5.7.246Removed external recipients that were not originally specified on submission.

  HVE accounts cannot send to recipients outside the organisation.