Guidelines for Administrators of
Penn E-mail Systems
On a campus with over 30,000 e-mail accounts like Penn, it
is important to consider the impact of e-mail on the total computing
environment. Mail messages affect computer systems and networks
in ways that message senders often cannot control and rarely
consider.
Administrators of large e-mail systems, by following
the guidelines below, can help reduce the unpredictable nature
of e-mail on the electronic environment. The guidelines should
be understood in the context of Penn's
Policy on Acceptable use of Electronic Resources
and current e-mail policy.
Maximum Size of Messages
| |
| Guideline |
To minimize potential service disruptions, all campus e-mail servers
should be configured to restrict the size of outgoing mail messages to a maximum
of 30MB. In addition, e-mail servers should be configured to reject incoming
messages that exceed this threshold.
|
| Notes |
Each recipient of a message usually receives a copy of the
message in a shared incoming mail area called the spool area. A large
message sent to only a few people can fill the shared spool area and prevent
additional e-mail from being received by users on that host.
The resulting denial of service to users can be caused inadvertently
or maliciously by the sender of a message.
|
Management of Mail Spool Area |
| Guideline |
To facilitate the management of individual users' e-mail environments,
all campus e-mail servers should be configured to exclude incoming mail
from a user's total disk quota, to limit spool areas to no more than 20MB,
and to issue warnings when spool storage exceeds 500KB for an individual
user. |
| Notes |
When individual disk quota's are enabled,
it is possible to configure the user's total quota to include or exclude
the incoming mail spool.
- If the server is configured to include the spool area in the user's
total quota, incoming mail will be rejected if new messages are sent that
exceed the quota, and individual users will be locked out of their
accounts and unable to make space available without intervention by a
system administrator.
- If the server is configured to exclude the spool area from
the user's total quota, limits are usually set on the size of an
individual's spool area and warnings are typically sent to users when
their incoming mail exceeds a pre-defined threshold. In this case,
users have the opportunity to make space available so that mail is
removed from the spool area.
The down side to this configuration
is a greater possibility that a user will receive e-mail that
disproportionately occupies the shared incoming spool area and
is unfair to other users. To make matters worse, some users
configure their POP e-mail clients to leave messages on the
server, further filling the shared spool area with additional
messages that are already read. Setting a relatively low threshold
for warnings mitigates this problem at the expense of being a
nuisance to the user.
Use of e-mail clients that download incoming mail to desktop computers
(via POP mail, e.g. Eudora) helps to reduce the pressure for more server
disk storage. However, creation of web home pages, as well as IMAP-based
mail (likely to become popular over the coming year) will increase the
pressure for more server storage space.
|
E-mail
Policy
Resource Rules
|
