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

  • Error: 550 relaying prohibited (or similar)
    Runbox’ SMTP server requires that your mail client supports authentication. All you need to do is to check “My outgoing server requires authentication” under Account properties (in Outlook, there are similar options in other clients). Select the option to use the same login data for the SMTP server as for the POP server.Note: Some older/smaller clients, and the older Opera mail client (version 6), do not support this.Eudora users on Macintosh computers need to follow the fix described here: http://www.eudora.com/techsupport/kb/2354hq.html
  • 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: Server could not be found, connection failed (or similar)
    Some ISP’s restrict outgoing mail sent through them, by prohibiting any third party servers from sending mail on port 25 (default). To circumvent this, you just need to specify in your email client that the port should be 26 for the SMTP server.
  • 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. This no longer applies starting 8 hours after you subscribe, though.