GMail for Non-GMail Users

There are a number of things that Non GMail Users need to
consider when sending mail to GMail users:

You don't know who is on G-Mail and who isn't.
You need to assume everyone is.
Mail Delivery is sometimes delayed.
Sometimes e-mail delivery is delayed. This occurrs frequently as the end of the work day approaches. Please allow adequate time for delivery.
Do not use HTML messages
A brilliantly composed Outlook message will fail spectacularly in GMail and be unintelligible. Compose complex, non-text messages in OpenOffice, Word, or Wordpad, and include them as attachments.
GMail is on a public server
Since GMail is on a public server do not send any sensitive or confidential information using mail. This is part of the security policy anyway ( What, you didn't know that? )
GMail users don't get notifications when mail arrives.
GMail users check mail at intervals without notifications. They may not get your meeting invite until after the meeting is over.