FAQ
I would like for members of the list I run to be able to
send HTML-encoded emails and any attachments except pictures.

"Remove message attachments that have a matching content
type" contains:
image

"Remove message attachments that don't have a matching
content type" contains:
multipart/mixed
multipart/alternative
text/plain
text/html

"Should Mailman convert text/html parts to plain text?" is NO

As a test I copied an HTML file that was open in Word (it
contained a single line), pasted it into Outlook (set for
HTML) and sent it to my list. I got the following repsonse:

"The attached message matched the
4sam-4seasonsatmapleton.org mailing
list's content filtering rules and was prevented from being
forwarded
on to the list membership. You are receiving the only
remaining copy
of the discarded message."

One of the attachments contained this:

BODY { MARGIN-TOP: 25px; FONT-SIZE: 10pt; MARGIN-LEFT: 25px;
COLOR: #000000; FONT-FAMILY:
Arial, Helvetica } P.msoNormal { MARGIN-TOP: 0px; FONT-SIZE:
10pt; MARGIN-LEFT: 0px;
COLOR: #ffffcc; FONT-FAMILY: Helvetica, "Times New Roman" }
LI.msoNormal { MARGIN-TOP:
0px; FONT-SIZE: 10pt; MARGIN-LEFT: 0px; COLOR: #ffffcc;
FONT-FAMILY: Helvetica, "Times New
Roman" }

Sunday, April 10, 2005

What am I doing wrong?

Thanks.

Search Discussions

  • Mark Sapiro at Mar 4, 2005 at 10:54 pm

    Pete Holsberg wrote:
    I would like for members of the list I run to be able to
    send HTML-encoded emails and any attachments except pictures.

    "Remove message attachments that have a matching content
    type" contains:
    image
    I don't think this works. I.e. I don't think 'image' will match all
    'image/*' content types. I think you have to enumerate all the
    subtypes, but all image/ types will be removed by the rules below
    anyway.
    "Remove message attachments that don't have a matching
    content type" contains:
    multipart/mixed
    multipart/alternative
    text/plain
    text/html

    "Should Mailman convert text/html parts to plain text?" is NO
    It looks like these settings should allow HTML, but they won't allow
    non-image attachments that aren't text/plain or text/html. Your second
    set allows only text/plain and text/html parts that are either the
    only part or a sub-part at some level of multipart/mixed or
    multipart/alternative parts. Also if a multipart/alternative part
    contains both text/plain and text/html parts only the first part
    (normally the text/plain part) will pass the filter.
    As a test I copied an HTML file that was open in Word (it
    contained a single line), pasted it into Outlook (set for
    HTML) and sent it to my list. I got the following repsonse:

    "The attached message matched the
    4sam-4seasonsatmapleton.org mailing
    list's content filtering rules and was prevented from being
    forwarded
    on to the list membership. You are receiving the only
    remaining copy
    of the discarded message."

    It doesn't seem like this should have happened, but see below.

    One of the attachments contained this:

    BODY { MARGIN-TOP: 25px; FONT-SIZE: 10pt; MARGIN-LEFT: 25px;
    COLOR: #000000; FONT-FAMILY:
    Arial, Helvetica } P.msoNormal { MARGIN-TOP: 0px; FONT-SIZE:
    10pt; MARGIN-LEFT: 0px;
    COLOR: #ffffcc; FONT-FAMILY: Helvetica, "Times New Roman" }
    LI.msoNormal { MARGIN-TOP:
    0px; FONT-SIZE: 10pt; MARGIN-LEFT: 0px; COLOR: #ffffcc;
    FONT-FAMILY: Helvetica, "Times New
    Roman" }
    The actual contents of a part are not relevant. The thing that counts
    is the part's Content-Type: header.

    --
    Mark Sapiro <msapiro at value.net> The highway is for gamblers,
    San Francisco Bay Area, California better use your sense - B. Dylan
  • Pete Holsberg at Mar 5, 2005 at 5:26 pm
    Thanks, Mark.

    I decided to create a test mailing list to experiment with
    content filtering. Incidentally, this is Mailman v2.1.5.

    Edit filter content: YES
    Filter mime types: (blank)
    Pass mime types:
    multipart/mixed
    multipart/alternative
    text/plain
    text/html
    Convert HTML to plaintext: (see below)
    Filter action: Forward to list owner

    I created a simple two-line HTML "page" in Word and pasted
    it in to Outlook (set to send HTML) but without stationery.

    It didn't matter whether "Convert HTML to plain text" was
    YES or NO: In both cases, all HTML font formatting was
    stripped out. However the link I had in the original was
    preserved.

    I'd be happy to email the simple test page to anyone off list.

    This is really confusing me!

    -----------------

    If my HTML page has an image in it ("stationery"), it will
    be treated as an attachment. Won't Mailman remove it because
    it doesn't have an approved content type? It doesn't.
    Instead it blocks the message and sends me this:

    "The attached message matched the XXX mailing
    list's content filtering rules and was prevented from being
    forwarded
    on to the list membership. You are receiving the only
    remaining copy
    of the discarded message."

    When I send the same page without the image, the message is
    acceptable.

    Thanks.
  • Mark Sapiro at Mar 5, 2005 at 5:46 pm

    Pete Holsberg wrote:
    I decided to create a test mailing list to experiment with
    content filtering. Incidentally, this is Mailman v2.1.5.

    Edit filter content: YES
    Filter mime types: (blank)
    Pass mime types:
    multipart/mixed
    multipart/alternative
    text/plain
    text/html
    Convert HTML to plaintext: (see below)
    Filter action: Forward to list owner

    I created a simple two-line HTML "page" in Word and pasted
    it in to Outlook (set to send HTML) but without stationery.

    It didn't matter whether "Convert HTML to plain text" was
    YES or NO: In both cases, all HTML font formatting was
    stripped out. However the link I had in the original was
    preserved.

    I think what's going on here is the original message is
    multipart/alternative with both a text/plain part and a text/html
    part. If more than one sub-part remains in a multipart/alternative
    part after filtering, Mailman selects the first remaining alternative
    which would be the text/plain part in this case.

    There are two ways to get the HTML part to the list in this case. One
    is to not allow text/plain at all. This is probably a very bad idea
    for a discussion list, but might be viable for an announcement list
    where the intent is to always post HTML. The other is to set up your
    MUA (Outlook) to send HTML only, not multipart/alternative.

    I'd be happy to email the simple test page to anyone off list.

    This is really confusing me!

    -----------------

    If my HTML page has an image in it ("stationery"), it will
    be treated as an attachment. Won't Mailman remove it because
    it doesn't have an approved content type? It doesn't.
    Instead it blocks the message and sends me this:

    "The attached message matched the XXX mailing
    list's content filtering rules and was prevented from being
    forwarded
    on to the list membership. You are receiving the only
    remaining copy
    of the discarded message."

    When I send the same page without the image, the message is
    acceptable.
    What this means is content filtering removed the entire message. This
    may be a problem with content filtering or it may be the way Outlook
    structures this message. I can't say without seeing such a message as
    received by Mailman. If you want to Cc: me directly with one of these
    test posts, I'll look at it and tell you what I think.

    --
    Mark Sapiro <msapiro at value.net> The highway is for gamblers,
    San Francisco Bay Area, California better use your sense - B. Dylan
  • Stonewall Ballard at Mar 6, 2005 at 7:56 pm

    On Mar 5, 2005, at 12:46 PM, Mark Sapiro wrote:

    I think what's going on here is the original message is
    multipart/alternative with both a text/plain part and a text/html
    part. If more than one sub-part remains in a multipart/alternative
    part after filtering, Mailman selects the first remaining alternative
    which would be the text/plain part in this case.
    This was a problem with my users until I discovered that Outlook seems
    to send the text part first, but other mail clients sent the html part
    first, so html was getting through only for people who didn't use
    Outlook.

    But I don't see the point of removing all but one alternative part. Why
    does Mailman do that?

    - Stoney
  • Mark Sapiro at Mar 6, 2005 at 8:38 pm

    Stonewall Ballard wrote:
    On Mar 5, 2005, at 12:46 PM, Mark Sapiro wrote:

    I think what's going on here is the original message is
    multipart/alternative with both a text/plain part and a text/html
    part. If more than one sub-part remains in a multipart/alternative
    part after filtering, Mailman selects the first remaining alternative
    which would be the text/plain part in this case.
    This was a problem with my users until I discovered that Outlook seems
    to send the text part first, but other mail clients sent the html part
    first, so html was getting through only for people who didn't use
    Outlook.
    This would appear to be a violation of RFC 2046 section 5.1.4 which
    says in part "... the alternatives appear in an order of increasing
    faithfulness to the original content."

    But I don't see the point of removing all but one alternative part. Why
    does Mailman do that?
    To reduce the size of the outgoing message. This can be a significant
    reduction.

    Also, to support the idea that posts received from mailing lists should
    be intelligible to the maximum number of recipients, some of whom may
    by choice or necessity not use MIME aware MUAs.

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

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