Note: For trial accounts you must validate the alternative email address you added to your account before you can send email with an email program.

The most common errors associated with sending mail through an email program are:

  • Error: 550 relaying prohibited (or similar)
    Runbox’ SMTP server requires that your mail program supports authentication. This means you must be sending your username and password for sending mail as well as receiving incoming mail. Email programs usually have two places where you have to enter your username and password, one for incoming mail and one for outgoing mail. Some programs have an option which says something like “use the incoming username/password for outgoing mail” which is also fine.
  • Error: 550 Administrative prohibition
    You are trying to send a message without SMTP authentication, or the message contains certain disallowed elements that indicate spam or phishing attempts.
  • Error: 550 Invalidated From address
    You are trying to send from an address that is not recognized by the Runbox system. You are only allowed to send from addresses that are among your Runbox aliases, virtual domain addresses, or external addresses explicitly validated via the address in question.
    To validate an external address, enter it in the Webmail Preferences for any Webmail folder and click [Save settings]. A confirmation message will be sent to the address, requiring you to click a link in the message to confirm that you own the address. Once validation is complete you can send from that address via Webmail or SMTP.
  • Error: (After sending a number of mails, delivery starts failing)
    If you are a trial user, you may not send more than 20 mails (i.e. to more than 20 recipients total), per day. The default limit for paid users is 500 recipients per day.