Relay Access Denied. Please help, I'm really stuck

I have two DigitalOcean droplets. DEV and MAIL, which is running MIAB.

When I attempt to send mail from DEV through MAIL, I get a “relay access denied error.”

> # telnet 25
> Trying xx.xx.xx.xx.xx...
> Connected to
> Escape character is '^]'.
> 220 ESMTP Hi, I'm a Mail-in-a-Box (Ubuntu/Postfix; see
> helo
> 250
> mail from: <>
> 250 2.1.0 Ok
> rcpt to: <>
> 554 5.7.1 <>: Relay access denied

How can I send mail directly from one server through the MIAB server?

Please help, I have no idea how to move forward.

Try using Mailgun or Sendgrid for SMTP relay/ Website transactional mails, instead (a FREE 10000 emails/mo or 100 mails/day account are normally enough to cover this kind of needs for all of your WEB server domains).

I’m here looking for help, not an advertisement. Shame on you.

My friend!.. SMTP relay doesn’t work through MiaB (I don’t know why :/)… My answer is not an advertisement… It’s just the single way you could try to achieve what you asked for.

@pbarney Cool it, please. @just4t is trying to help. Mail-in-a-Box is not normally meant to be a SMTP relay and this forum isn’t for asking for basic system administration help.

To use Mail-in-a-Box as an SMTP relay, you’ll need to configure your server to connect in the same way a mail app would — the documentation for that is in your box’s Mail-in-a-Box control panel. We also have some notes at

Thanks! @JoshData . No doubt provided info. may help me, too in future system builds.