[Mailman-Users] pass mime types

Mark Sapiro mark at msapiro.net
Sat May 10 01:15:55 CEST 2008

Rueben wrote:

>I don't understand your answer.

Apparently because you don't understand MIME. You could start at
<http://www.imc.org/rfcs.html#mime>, but that probably isn't the
easiest way to learn these things.

In my explanation below, indententation is the key. When I wrote for


I was indication a message with content-type multipart/mixed which
consisted of two sub-parts of types multipart/alternative and
application/msword, and the multipart/alternative sub-part in turn
contained text/plain and text/html alternative sub-parts

You may also be interested in
<http://www.iana.org/assignments/media-types/> which is a list of
registered MIME types for various content.

>Let me ask it differently.
>What would the mime types look like if I wanted to allow attachments for PDF 
>and image files?

Pass mime types might contain


Line by line, the reasons are

1. If you don't accept multipart then the only messages you accept will
be single part messages which by definition do not have attachments.

2. Accepting message/rfc822 is not manditory, but if someone forwards a
message as an attachment, and you want to at least consider the parts
of the attached message, you need this.

3. This is to accept plain text message bodies and attachments.

4. This will accept all 'image' content-types. if you want to be more
selective you could accept, e.g., just image/jpeg, image/gif and
image/png by listing those instead of the blanket 'image' (refer to
the media types list referenced above).

5. This will accept PDF.

>Would it be any different if I wanted to allow html links to other websites?

If you want to allow html parts, you have to add


to the above list. I'm not sure what you mean by "html links to other
websites". I included two URLs above in this text/plain message. Some
MUAs (mail clients) may render these as clickable links. Others may

>----- Original Message ----- 
>From: "Mark Sapiro" <mark at msapiro.net>
>To: "Rueben" <roobin at theriver.com>; "Mailman-user" 
><mailman-users at python.org>
>Sent: Saturday, May 03, 2008 10:11 AM
>Subject: Re: [Mailman-Users] pass mime types
>> Rueben wrote:
>>>Under content filtering there is a field labeled: Remove message 
>>>attachments that don't have a matching content type.
>>>In the box I have:
>>>Can someone explain what each of those entries means, and give examples as 
>>>to what kind of files would be affected by each filter?
>> Those entries are the MIME content types that content filtering will
>> accept. Any message part with a content-type other that those three
>> will be filtered out. For example, in a message with the following
>> structure
>> multipart/alternative
>>    text/plain
>>    text/html
>> The multipart/alternative part will be accepted and it's sub-parts
>> examined. Of those, only the text/plain part will be accepted and the
>> text/html part will be removed.
>> For this message
>> multipart/mixed
>>    multipart/alternative
>>        text/plain
>>        text/html
>>    application/msword
>> again, only the text/plain part will be accepted and the text/html and
>> application/msword parts will be removed.
>> For this message
>> multipart/related
>>    multipart/alternative
>>        text/plain
>>        text/html
>>    image/jpeg
>> nothing will be accepted because the entire multipart/related message
>> content type is not accepted.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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