The MIME standard for e-mail content, launched in March 1992, changed Internet communications from plain-text messaging to a multimedia workhorse.
It was 20 years ago that MIME taught e-mail to play.
The Multipurpose Internet Mail Extensions enabled interoperable formatting of multiple media and character types within the Simple Mail Transfer Protocol for the first time, allowing images, sound and applications to be sent by e-mail. Adoption of this standard helped to change Internet communications from plain-text messaging to a multimedia workhorse.
Some of the original Bellcore developers of the standard gathered March 5 to commemorate the sending of the first MIME e-mail attachment: An audio file of a barbershop quartet singing “Let Me Send You Email” to the tune of “Let Me Call You Sweetheart,” along with a photo of the quartet and a copy of the song’s lyrics.
That event on March 11, 1992, widely expanded not only the functionality of e-mail but also its geographic reach, said Nathaniel Borenstein, one of creators of MIME. At that time, e-mail supported only s7-bit plain ASCII text, which defined only letters in the Latin alphabet without diacritical marks. That was fine for English, Borenstein said, but “hardly anything else fits that description.”
By supporting the interoperable encoding of other types of characters as well as other media, e-mail was able to cross language and technical barriers for the first time, going from a proprietary regional hack to a global tool.
“It took it from something a geek could do to something anyone could do,” Borenstein said of the support for both multimedia and multi-character. “One of the things we did right was to combine the two. It made less difference to Americans than it did to other people in the world” when it was first introduced.
Borenstein now is chief scientist at Mimecast, an e-mail management company.
MIME was developed by computer scientists at Bellcore, the research arm of the old Bell operating companies that since has gone through a number of corporate iterations to emerge most recently as Applied Communications Sciences. Because SMTP was such as bare-bones standard, there were a lot of proprietary implementations, some of which included their own technology to encode non-ASCII content.
The need to make it backwards-compatible with existing products made developing MIME like threading a needle, Borenstein said. “There were a whole lot of constraints,” in providing new functionality without interfering with existing features. “It was more of a social and political accomplishment than a technical one.”
MIME today comprises six Internet Engineering Task Force memoranda, extending SMTP to support additional formats.
“The core of it has been very stable,” Borenstein said, but it has expanded to include many new media types. The original specifications defined 16 types. Today there are more than 1,300 media types registered with the Internet Assigned Numbers Authority. Media are divided into eight top layer types, such as text and image, with multiple subtypes under each. The largest category is application, which contains many distinct subtypes from individual vendors.
After 20 years, MIME is still on version 1.0. But that is not because the initial version was perfect, Borenstein said. It was intended to evolve as it expanded, but has been stuck on 1.0 because there was not adequate specification on how to handle future versions.
Another mistake was the content disposition header. The original specification did not address presentation styles and differences between inline data and attachments that are not displayed automatically were not clearly defined, Borenstein said. Today, different platforms still handle this differently.
“We’re darn lucky we don’t have to change it,” Borenstein said, because MIME is so deeply embedded in the Internet that significant changes to the protocols would be difficult today.
He likened shifting to a new e-mail protocol to the shift from Version 4 of the Internet Protocols to IPv6, a move now under way only because it is being forced by the exhaustion of IPv4 addresses. Without a similar imperative, it is unlikely that MIME will be significantly changed in the foreseeable future, he said.
Of course, it has not been all good news since the development of MIME. Features that have legitimate uses have also proved attractive to the bad guys, making e-mail an effective delivery vector for a variety of malicious activities. Symantec Corp. reported in its February Intelligence Report that spam accounted for 68 percent of e-mail, and phishing made up 0.28 percent of all e-mail traffic. One in 274 e-mails contained some kind of virus.
“That’s a problem I’ve spent a goodly part of my subsequent career thinking about,” Borenstein said.
But he pointed out that spam, phishing and many other attacks could be carried out without MIME. Beating the e-mail scam artists will always be difficult because it is an asymmetric activity that requires a lot less effort to perpetrate than to block.
“Spammers don’t have to do much to get ahead,” he said. There are tools to thwart malicious e-mail, but because of advances in computing power, “even if we implement them all, we will still be behind. It’s a hard problem.”
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