Gmail functionality was developed in order to meet the very exacting requirements of the X.400 standard for e-mail clients and transfer protocol. X.400 has been largely outcompeted by the Internet e-mail standard (SMTP) in the general e-mail market, but the functional requirements remain widely acknowledged as a standard to which e-mail systems aspire. Gmail offers, and retains between Gmail users all of the functions defined in the X.400 standard, and more.
Fully functional mail:Gmail provides all mailing functions such as: create, forward, retransmit and reply to a message. It also supports all messaging options such as: delivery reports, receipt notifications and the various options for timing such as: delayed delivery, request for a reply before and message expiry time and date.
Personal filing system:Gmail puts incoming mail into your incoming folder, keeps copies of messages you have sent in your outgoing folder, and messages you have deleted in your trash folder. You can create as many additional folders as you wish, and store messages by topic or other criteria.
Comprehensive message status display:Gmail displays the status of each of your messages: Message has attachment, Reply made, Message is unread, Please reply to this message, Acknowledgment requested.
Unlimited attachments:Gmail allows you to attach any number of documents and files to a Gmail message, each of a size limited only by available space. Any word processing document, spreadsheet, graphic image, or program that can be stored on a computer can be attached to a Gmail message and sent with the message.
Full range of send options:Gmail offers all X.400 send options and more; for example: request receipt notification and delivery report, set sensitivity, importance and priority level, request reply, and defer message delivery until a specified date and time.
Send message with warning:Gmail can be requested to notify the recipients when the message has arrived, even though the recipients are using other applications. If you iconize Gmail while working with other applications, the icon will change form, and come into the foreground whenever you have unread mail. It will not otherwise disturb your work, unless you configure Gmail to warn you for each message.
Complete acknowledgment status:Gmail generates and accepts delivery reports and receipt notifications as required by X.400. You can request acknowledgments: always, only if error, or never; both by your personal default setting and for each individual message. Acknowledgments are correlated with your copy of the original message, so by looking in your outgoing folder you see the status of your messages, for example: Acknowledgment is requested, One or more positive acknowledgments received, One or more negative acknowledgments received or Positive acknowledgments received from all. A detailed status report is available, and displays the message status for each individual recipient.
Mail Application Programming Interface (MAPI):Gmail has its own implementation of simple MAPI so that Windows application that has used simple MAPI to integrate themselves with e-mail will operate in a Gmail environment.
Gmail Application Programming Interface (GMAPI):Gmail API can be used on all platforms supported by Gmail (MAPI is Windows-specific). Your Windows, UNIX and Linux programs can all use this API to integrate themselves with e-mail.