Can an HTML email body reference a file sent as an attachment (in the same email)?

Question

Can an HTML email use an image attachment as the source for tag?

Let's say I am sending an email with per-email specific images - and they are sent as an attachment to the email - can the HTML body within the email use the those images? My guess would be no, but are there any hacks or workarounds that would make it work?

Thanks,

Solution

No hacks needed. Use the cid: URI scheme

 --boundary-example 1
 Content-Type: Text/HTML; charset=US-ASCII

 to the other body part, for example through a statement such as:
 <IMG SRC="cid:foo4*[email protected]" ALT="IETF logo">

 --boundary-example-1

 Content-ID: <foo4*[email protected]>
 Content-Type: IMAGE/GIF
 Content-Transfer-Encoding: BASE64

 R0lGODlhGAGgAPEAAP/////ZRaCgoAAAACH+PUNvcHlyaWdodCAoQykgMTk5
 NSBJRVRGLiBVbmF1dGhvcml6ZWQgZHVwbGljYXRpb24gcHJvaGliaXRlZC4A
 etc...

 --boundary-example-1--

Comments

[Jonathan]

I take it the carets are necessary? Content-ID: < name >

[Quentin]

from the documentation linked to in the answer: "Notes: In Internet mail messages, the addr-spec in a Content-ID [MIME] or Message-ID [822] header is enclosed in angle brackets (<>)."

[Sandburg]

why is the data in base64? It is user defined and needed, or can it be different or inrelevent in that case?