VPIM is based on existing Internet Mail specifications. It wraps encoded voice messages in MIME message parts, and uses SMTP to transport them over TCP/IP networks. The VPIM profile requires that these multi-part messages be formatted and used according to a specific set of Internet conventions and rules, and it's predictability enables voice mail servers to automatically and correctly handle messages and their constituent parts.

The profile is intended to facilitate server-to-server message exchange, especially between voice message systems from different vendors. It does not define how servers are to present messages to either end users or client applications, because some voice servers will use telephone interfaces, others may support email client protocols such as POP3 or IMAP4, while still others are likely to find additional client protocols appropriate to their applications.

VPIM messages are made up of one or more parts, at least one of which must be a voice message, and all of which are MIME encoded. The profile also allows for optional, additional MIME parts for spoken name, forwarded messages and fax messages, and an electronic business card data definition, that allows automatic updating of directory information with phone number, text name or email address.

VPIM voice message parts are encoded using the ITU's G.726 32-kbps ADPCM standard. G.726 was selected because it has no royalty fees or intellectual property rights, is compatible with the earlier AMIS-D standard, has toll quality sound and is of a reasonable size when compressed (320 Kbytes per minute of MIME-encoded voice messages using SMTP, 240 Kbytes using binary ESMTP). Other voice encoding algorithms exist, and systems communicating via VPIM can arrange, via prior vendor agreements, to use them. As other encoding standards, such as the G.723.1 standard recently selected by a group of Internet telephony developers, are proven in the market, VPIM could be extended to include them.

VPIM fax encoding is based on the TIFF-F specification, while the electronic business card format is based on the Internet adaptation of the Versit Vcard specification. Vcard information stored in a directory can be made available to applications including voice mail, fax and email.

The first VPIM RFC (RFC 1911) was published in 1996 and formed the basis for trials and testing. The experience from these trials as well as feedback from other participants was incorporated into the Standards Track VPIMv2 RFC (RFC 2421) that was published in 1998.