email, the g.cs.miami.edu and m.cs.miami.edu placeholder domains

July 4, 2017

Email for the department is generally addressed to the domain cs.miami.edu. The remainder of this post is for those curious about the department’s email routing, or special cases were it is important to know more about our email routing.

By Internet standards, email is routed to a machine based on the domain portion of the email address, matched against an MX record entered into the Internet wide DNS database. Email is often relayed several times before it arrives at a machine tasked with dropping the email text out of the SMTP protocol into a local delivery mode, such as mbox, webmail, POP or IMAP. While A records and CNAME DNS records can be significant, the MX record is the most customary way to route email.

all mail:
   cs.miami.edu -MX-> corsair.math -etc/alias-> g.cs -MX-> gmail

if then to the faculty unix machine:
   gmail -forward-> m.cs.miami.edu -MX-> ewell.cs.miami.edu

The MX record for cs.miami.edu directs mail for that domain to the machine corsair.math.miami.edu (this will change soon). Corsair can be considered the gateway into the departmental mail system. The machine provides spam filtering, mailing list bursting, and a switchboard for forwarding mail. A few users forward from corsair using .forward files in their home directories, but this is now very discouraged, and the possibility of forwarding using .forward files will disappear. Forwarding is done by corsair:/etc/aliases.

It is strongly encouraged that all forwarding from corsair be to g.cs.miami.edu. g.cs is a placeholder for mail going to the departments Google Docs gmail system. The name g.cs.miami.edu is MX’ed to the various google mail servers according to Google Docs requirements.

On arriving at the gmail server, the department believes the mail as reached its destination. However, some users continue to prefer traditional command line unix mail. Hence it is possible to forward mail from gmail to a departmental email server using the name m.cs.miami.edu. Currently, m.cs.miami.edu is an MX to ewell.cs.miami.edu, the machine that provides centralized computer services for department faculty.

Ewell is setup to use the department’s gmail server as an SMTP server for all outgoing mail.

Historial

The history of email at the department predates the first internet service in the South Florida region as it was a UUCP hub, which routed email hop-by-hop by scheduled telephone calls between UUCP hubs. e.g. this UUCP map of Florida. Internet arrived on the South Florida mainland via a satellite downlink to RMAS on Virginia Key, then running by an Ungermann-Bass Vitalink modem to the Physics Department on the 4th floor of the Ungar building.

The SMTP system then gradually replaced UUCP. The machine corsair is the descendant of the SMTP servers that have handled email for the cs.miami.edu and math.miami.edu domains for over 30 years.

Gmail for the department went live July 22, 2009. This service was a result of the ITAC responding to the then-Provost’s request to explore the viability of Google as an email provider, e.g. the ITAC minutes of March 31, 2009, April 22, 2009 and May 9, 2009. The department has phased it on over time, and the policy now, with a few exceptions, is that all departmental email be destined to and originate from, the gmail service.

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