Draft Policy on Permissible Email Attachment Size
Working Draft For Public Review and CommentsThis Draft Policy Guidance is being made available for public review and comments
until 1 August 1998. Comments may by sent by Email to artch.griffin@gsa.gov
or regular mail to: General Services Administration Attn: Artch Griffin (MK), Room 2239 1800 F Street, NW Washington, DC 20405
CIO Council - Interoperability Committee
Federal Email Postmasters Working Committee
CIO Council Recommendation for Agencies' Policy on Permissible Interagency Email and Attachment Size
Draft - Version 3
1. Email is provided to enhance the performance of Government. Unnecessarily large Email messages or Email with unnecessarily large attachments create congestion within and between Agency Email systems. This congestion results in long delays and unnecessary costs for the storage and transport of Email. Just a few excessively large messages can create a number of Email delivery delays and other "performance" failures for many users not only on your agency's Email system but on other's systems as well.
2. To help manage the potential for Email system congestion (and some type of denial of service attacks), controls on interagency and extra-governmental Email size should be considered. The following Technical Operations Guidance is offered:
A. The collective experience of the Federal Email Postmasters Council suggest that agencies are able to accommodate interagency and extra-governmental exchanges of Email (including attachments) of up to 5 megabytes. Agencies, therefore, should configure systems to accommodate Email up to 5 megabytes, and are encouraged to set limits within their systems to prevent larger Email from being routinely transmitted outside. Your agency is encouraged to adopt this limit so as to accommodate end-users expectations and to provide for a level of consistency among government agencies.
B. Insure that your agency's Message Transport Agent (MTA) is a version that support the SMTP Service Extension for Message Size Declaration (i.e., "SIZE="). See Internet Engineering Taskforce (IETF) Standard 10. This will allow your system to reject large Emails before they are sent to (and congest) your agency's system. It will allow others to reject large Emails from your agency. (Technical Note: For "sendmail" based MTAs, check the MAXSIZE option and also the "M=" equate setting for the local delivery agents.)
C. Assuming that your agency is using "sendmail" version 8.7 or later, consider using the command-line switch "-R hdrs" so that receiving sites (using ESMTP) will only return the headers of a rejected Email in any bounced mail notifications. This prevents large attachments from bouncing around among several Email systems in the event of a delivery problem. This capability is part the Delivery Status Notification described in IETF RFCs 1891-1894 and other MTAs may support the feature as well.
D. Consider configuring your agency's MTA so that over sized Emails, if sent, are placed in a deferred queue for attempted delivery during off-peak periods. The SMTP "Precedence" header line can be used to establish the mail queue processing priority in most MTAs.
E. While different agency missions require the transmission of information of various sizes and Email may be an appropriate means, consideration should be given to alternatives. For example, files or documents intended for wide distribution could be placed on a Web server. Then the Uniform Resource Locator (URL) for the file could be sent via Email or otherwise posted. The URL could be either the Hypertext Transport Protocol (http) or the File Transport Protocol (ftp) version.
Background: Discussion at the Federal Email Postmaster's Council on "systems performance" and Email delivery delays focused on the problems associated with excessively large Email that create congestion and significant delivery performance problems. It was observed that many of the "large" Emails appear to be exchanged between governmental sites and non-governmental addresses. A suggested policy position on "Approved Uses of Email" has been drafted. This Technical Operation Guidance is offered as an approach to providing a consistent Governmentwide position on message size and to point to some tools of implementing operational controls.
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