First answer: identify where the address was rejected
A 550 5.1.1 bounce normally says the rejecting mail system did not recognise the destination mailbox address. It does not prove that the sender used the wrong spelling or that a mailbox is absent at the provider you intended. Read the full delivery-status notice to find the rejected recipient and the server that replied. Then compare that server with the domain’s intended mail host. Changing SPF, DKIM, the website address or a mailbox password will not repair a recipient-address rejection by itself.
This guide is for a domain whose accepted Novasean service includes DirectAdmin mail. A website hosted in DirectAdmin may still receive mail at Microsoft 365, Google Workspace or another provider. In that case, the external mail operator owns the rejected recipient; a DirectAdmin mailbox is not the receiving mailbox merely because it appears in the hosting panel.
Read the bounce before touching the configuration
- Confirm that you actually sent the failed message. If you did not, check your Sent folder and account activity; a forged sender address can also cause an unrelated bounce.
- Record the exact failed recipient, the time and time zone, the
550 5.1.1wording and anyRemote-MTA, rejecting-host orDiagnostic-Codefield. A notice may say “in reply to RCPT TO”; that identifies the SMTP stage, not the correct repair. - Check whether the address was mistyped, including an old domain, alias or punctuation. Ask the intended recipient through another known channel if the address is still valid. Do not resend a sensitive message until the destination is confirmed.
For example, a notice naming team@example.com and “user unknown” at mx.old-provider.example points first to the destination and mail route. Both names are illustrative. It does not justify creating team in DirectAdmin if the domain is meant to use the old provider or if the old MX was supposed to have been retired.
Compare the rejecting host with the intended MX route
Check the authoritative MX records for the recipient domain, then compare their targets with the mail provider specified for this service and with the rejecting host in the bounce. A recursive check such as dig MX example.com +noall +answer is useful, but it can show a cached answer; use the authoritative DNS guide to confirm the live source. If MX names an external provider, investigate the address there. If MX names the DirectAdmin mail service, check the local recipient in the correct DirectAdmin account. During a recent migration, an old sender may still use a cached MX route, so compare timestamps and the previous TTL before changing anything.
MX answers route internet delivery but do not prove that the receiving server accepts a domain or a particular mailbox. DirectAdmin’s Local Mail Server setting is a separate control. If the domain is deliberately remote, leave it remote. If the route and local-domain state disagree, ask the responsible mail operator to check them; do not flip MX or local delivery to silence one bounce. The relay-rejection guide covers the distinct case where the server refuses to relay or an unauthenticated client cannot submit mail.
Check the exact mailbox, alias or forwarder at the intended provider
If DirectAdmin is the intended receiving service and your account permits mail management, select the correct domain at User level. In E-mail Manager, check whether the exact local part exists as an E-mail Account, Forwarder or other configured address. Panel labels can vary by skin and entitlement. A forwarder can accept the first address yet fail at its downstream destination, so read the full notice for which address was rejected. The automatically displayed DirectAdmin system account is not a substitute for a customer mailbox with the same-looking name.
Do not delete and recreate a mailbox as a diagnostic shortcut: it can disturb stored mail and access. Do not enable a catch-all simply to accept a mistyped address; it may collect unintended mail and conceal the real error. If the address should exist but the panel and rejection disagree, ask Novasean support to trace the exact SMTP transaction and account mapping. Server logs, Exim routing and any repair of the mail platform belong to the authorised operator, not to a customer without server administration rights.
Verify one corrected route and preserve the evidence
After the responsible owner makes the specific correction, ask an external sender you control to send a new, harmless message to the exact address. Confirm that the sender receives no rejection and that the message actually appears in the intended mailbox or final forward destination. A server accepting a message is not proof of final placement. Repeat from a second sender only if the original sender still fails, because cached routing or sender-specific policy may differ.
Give support a redacted copy of the status code and diagnostic line, recipient domain, rejecting hostname, send time with zone, intended mail provider, authoritative MX result and any approved change already made. Do not include passwords or a private message body. The recipient-domain owner and actual mail operator decide whether an address should exist; Novasean can investigate only the service and controls within the accepted Order.
Common questions
Does 5.1.1 mean my mailbox is full? No. RFC 3463 defines X.1.1 as a bad destination mailbox address; X.2.2 is the mailbox-full code. Read the complete notice because a provider’s wording may add context.
Should I change MX to Novasean? Only if the authorised mail migration plan says Novasean is the destination and every required recipient is ready. A website hosted here can legitimately keep external MX.
Why does the address work for some senders? Compare the rejecting hosts and times. Cached old routing, an alias or a downstream forward can produce different results. Ask the mail operator to trace both paths before making another change.
Does passing SPF or DKIM fix this? No. Those mechanisms concern sender authentication. A recipient-address rejection needs an address and routing check first.
Sources and technical references
Related guides
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