WHY IS INCOMING EMAIL SOMETIMES DELAYED? WHERE IS MY MAIL? SDF has used UUCP (UNIX to UNIX CoPy) to transfer both incoming and outgoing mail since the late 1980s. This is referred to as a 'Store and Forward' method, so it is not always instantaneous. SDF does receive email directly using SMTP, but at the same time also uses a secondary host which queues up email via UUCP for pick up each hour via 'uucico' using the 't' protocol. The result: sometimes you get your mail in a few seconds, sometimes you have to wait a bit. This also means that if for some reason the primary SMTP server at SDF is down, offline for maintenance or on fire, email will still be written to an SDF UUCP queue for future delivery rather than sit waiting in a foreign outbound SMTP queue where it may be deleted or returned. All SDF hosted email domains use the SMTP primary and UUCP secondary MX (Mail eXchanger) method with the except of VHOSTed domains which have the option to use the UUCP secondary via 'mkvhost'.