Sitemorse checks urls for syntax and passes requests to the appropriate mail servers, stopping short of actually sending an email. If any error messages are received from the mail servers, they are recorded.

As Sitemorse checks all mail servers for any given mailto: url, it may uncover problems that are not immediately apparent. Emails are passed to the first mail server that will accept them. The mail servers are prioritised such that the primary server gets the first opportunity to handle the mail, followed by the secondary then tertiary and so on.

Therefore if there is a problem with the tertiary mail server it will remain unnoticed until there is, for example, a high volume of emails occupying the primary and secondary servers and emails fail to be delivered. Undelivered emails do not always raise immediate error messages to the sender and in most cases the recipient is completely unaware that emails are missing. It is not possible to check that an email address is functioning correctly simply by sending emails to it.