Although rare, on some occasions messages can be returned undelivered. This is sometimes immediately after sending but can also be after a few hours or even days.

There are a number of reasons why a message might be returned. Some of the most common are below:

  • mailbox/email address no longer exists
  • mailbox is full
  • recipient email service believes your message was spam
  • email service is currently unavailable (usually for this problem mail will be queued and another attempt at delivery will be made later)
  • the recipients mail service has blocked the Runbox mail servers

If mail is repeatedly returned undelivered please get in touch with Runbox Support. Please copy and paste the exact text of the error message you get back in to your message to us so that we can try and work out what happened.