Tags: Trends

MailChannels is pleased to announce the introduction of a new mail standard, one that is sure to spark joy for mail system administrators.  Read below for the details.

1. Introduction

SMTP replies are used to communicate information about the result of a command to clients. They are usually processed automatically by mail server software. Human users most often encounter them Delivery Status Notifications, as described in RFC 3464 [RFC3464], or in mail server logs. These messages are usually terse, often inscrutable, and always consist entirely of plain text. This proposal allows server operators in inject multimedia content into SMTP replies. This will make the replies both more informative and entertaining, as well as providing additional business opportunities to mail server operators.

2. Format of Multimedia SMTP Replies

Multimedia is added by appending the string '?=' (the ASCII character '?' (hex 3F) followed by ASCII character '=' (hex 3D)). That sequence is followed by the media type, as described in RFC 6838 [RFC6838], and the character '?'. After this character, the multimedia item data is appended, encoded in base 64 as described in RFC 4648 [RFC4648]. The reply MUST NOT contain any non-whitespace characters after the multimedia item data.

3. Display of Multimedia SMTP Replies

The user agent that displays the Multimedia SMTP Replies SHOULD render the multimedia item after the status code, but before the text part of the reply. Not all media types are practical to render on all interfaces, however, the user interface SHOULD support the following media types: - image/gif - image/png - video/mp4 - audio/mpeg Video and image items SHOULD be rendered at their original resolution. However mail server software SHOULD NOT include very large images or video in the reply, in order to make it easier to display in all interfaces. Video and audio multimedia items SHOULD start playing immediately when the reply is rendered in the user interface.


Friendlier Rejections

550 Computer says no

Revenue Enhancement

550 Message rejected. Try MailChannels™ for enhanced deliverability.


Try it Yourself

Paste a correctly formatted SMTP Multimedia Reply in the text box below and click render to see what it might look like in a user interface.

Search the Blog

    Subscribe To Our Blog

    What is an Outbound SMTP Relay Service?