Why Am I Getting “550 Authentication is Required for Relay”?

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Short answer: Your mail program is not signing in before it sends. Tick “My outgoing server (SMTP) requires authentication” and set it to use the same username and password as incoming mail. Mail will send immediately afterwards.

Applies to: Infosaic web hosting email · Outlook, Apple Mail, Thunderbird, phones and tablets

This is the most common email error we see, and it is reassuringly boring: nothing is broken, and your account is fine. The server is declining to pass your message on because it does not yet know who you are.

“Relay” means asking a mail server to deliver a message to somebody else’s domain. An open relay — one that does this for anybody — gets abused by spammers within hours and lands the entire server on blacklists. So our servers ask you to sign in first, every time. Receiving mail already involves a sign-in, which is why incoming works while outgoing fails.

How to fix it in Outlook

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Open File → Account Settings → Account Settings.
Select the account and click Change.
Click More Settings.
Open the Outgoing Server tab.
Tick My outgoing server (SMTP) requires authentication.
Leave Use same settings as my incoming mail server selected.
Click OK, then Next to test, then Finish.

The same setting on other programs

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iPhone and iPad. Settings → Mail → Accounts → your account → SMTP → the primary server. Fill in the username and password even though iOS labels them optional. Leaving them blank is exactly what causes this error.
Android. Account settings → outgoing server settings → turn on Require sign-in, then enter your full email address and password.
Apple Mail on a Mac. Mail → Settings → Accounts → Server Settings → Outgoing. Set authentication to Password and fill both fields.
Thunderbird. Account Settings → Outgoing Server (SMTP) → Edit. Set authentication method to Normal password and enter the full address as the username.

The username must be the full email address. Authentication can be switched on and still fail if the username is only the part before the @. Enter [email protected], not you.

If it still will not send

Check the username again. Full email address, and watch for a trailing space if you pasted it.
Try the alternative outgoing port. Some home and office networks block port 25 outright. Use port 8383, or the SSL port 465 with the connection type set to SSL.
Confirm the password. Sign in at webmail.infosaic.com with the same address and password. If webmail rejects it, the password is wrong; if webmail accepts it, the fault is in your mail program.
Check both places. Some programs keep a separate outgoing server entry shared between accounts. Changing one account may not have touched the server the failing account actually uses.
Send a test from webmail. If webmail sends and your program does not, the account is healthy and it is purely a settings problem.

Questions and answers

What does “550 Authentication is Required for Relay” mean?

The mail server declined to send your message because your program did not sign in first. It is an anti-spam protection, not a fault with your account.

How do I fix it?

Turn on the setting that says your outgoing server requires authentication, and set it to use the same username and password as incoming mail.

Why can I receive mail but not send it?

Receiving already requires a sign-in, so it works. Sending needs its own authentication setting, and that is the one that is off.

Why does the server require this at all?

A server that relays for anyone is abused by spammers almost immediately and gets blacklisted, which would stop everyone hosted on it from sending mail.

I turned it on and it still fails.

Check the username is your entire email address rather than just the part before the at sign, and that there is no trailing space.

Could my network be blocking it?

Yes. Some networks block port 25. Try the alternative port 8383, or port 465 with SSL.

How do I know whether the password is right?

Does this affect my phone as well?

Yes, every device needs the setting. On iPhone in particular, fill in the outgoing username and password even though they are labelled optional.

Still stuck?

Open a support ticket from your hosting control panel at controlpanel.infosaic.com — that is the fastest route, because it reaches the team who can already see your account. Please include the exact error and which mail program you are using.