[ARIN-consult] Consultation on Prohibiting Attachments on ARIN Mailing Lists

Jimmy Hess mysidia at gmail.com
Wed May 2 10:15:58 EDT 2018

On Tue, Apr 24, 2018 at 7:21 AM, ARIN <info at arin.net> wrote:
> ARIN has received a suggestion requesting attachments be prohibited on
> ARIN public mailing lists, including PPML.
> * Question:  Should attachments be prohibited on ARIN public
> mailing lists?

No.     Well,  first of all  technically  all components of a MIME email
can be described as an attachment:   Don't break expected features
without good justification

File attachments have legitimate purposes,  for example
as mentioned GPG/PGP message signing --  alternative  plaintext versions of
messages sent in HTML or RTF format.

> * Question:  If yes, should this include all ARIN public mailing
> lists, or only select lists?

No.    Attachments are commonly used with e-mail,  and the standard
feature should
be supportable,  but  I suggest regulating  file attachment usage  for
situations where
they  pose a risk of harming participants or  exclusing people from a

GPG message signing is common:   Attachments containing metadata about
other parts
of a message are harmless  providing they are  not useful for
malicious purposes,
and they are of a reasonable size.  100 Kilobytes is de-minimis.

I'm not sure what resources are available to run ARIN lists,   but
these days most services
provide  25-Gigabyte or larger mailboxes,  and  all the major ESPs
will handle 50 Megabyte objects,
so   even 1 Megabyte attachments  are widely considered de-minimis.

Example  of  reasonable restrictions on attachments:

(1) Filter attachment types so as to exclude  executables,   archive
files such as ZIP/RAR
and documents which  are DRM restricted, encrypted, or in a closed or
file format,

Example: Microsoft Word Documents are in a closed format;  require a proprietary
operating system to view  --- Should not be used on a public
discussion list,  since not
everyone has the necessary expensive or closed-source software,  and
that unfairly
excludes some people from participating  in discussion or accessing
information that should be
publicly available.

(2).  Replies -   When replying to a message on the list;  Don't
duplicate the original attachments.
Don't attach files that are available from another source:   provide a
link to the source, instead.

(3).  Large documents   (Bigger than 1 MB)  --   Don't send.   If it
is highly-pertinent or necessary to
the discussion then send a durable download link instead  of attaching
the file into in an e-mail message.

(4).  Unrelated Files -  Message parts that add up to larger than 100K  must
be related to specific  on-topic discussion.    Do NOT attach a graphic such as
a GIF or JPEG for use in an e-mail signature,  for comedic or
promotional reasons;
graphics should provide  diagrams or other visual information related
to the topic.

> https://www.arin.net/participate/mailing_lists/index.html

> John Curran

More information about the ARIN-consult mailing list