49 - September 2006
on Sending Emails to a Large Number of External Users
times, most departments may have genuine needs of sending
email to a large number of external recipients, and yet quite
a number of such email was either bounced as undelivered email
or returned with undeliverable notifications by the recipients'
email servers due to the following reasons:
email recipient lists were outdated (e.g. the recipients'
email addresses are invalid)
size of the email attachment was too large, resulting in
the email being rejected by the email servers at the recipients'
the number of such bounced email or undeliverable email notifications
was so huge (as the email is often delivered at the same time)
that it jammed our email servers, causing prolonged sluggish
email delivery. Worse still, complaints were received to ask
the CityU to stop sending the email for reasons such as the
recipients considered it as spam mail, or the email attachment
caused the recipients' email disk quota severely depleted,
resulting in their subsequent incoming email being missed.
departments have to exercise care when sending email to a
great number of external recipients. Moreover, it can also
devastatingly damage the image and the operation of the University
if this kind of email is sent without prior consent of the
recipients. For example, if some recipients do make complaints
to those Real Time Spam Black Lists (RBL) sites and have the
university email server being successfully blacklisted, no
CityU users will be able to send email to all those organizations
that are using the RBL as a means to fight spam mail. Besides,
it is also undesirable to send unsolicited email with an attachment
as the recipients may not know who you are and whether your
attachment is safe to open. If however you do have to send
an unsolicited email with an attachment, please limit the
size of the attachment to a minimum as the acceptable size
limit of an email message for many email systems is well below
In order to safeguard the reputation of the University, it
is advisable to adopt the following guidelines for good practice:
matter how small the number of recipients is, avoid sending
commercial advertising material without their prior consent.
sending email to a large number of recipients without their
prior consent and always keep an updated mailing list. Make
a plan beforehand to obtain their prior consent and collect
their email addresses, say, during an activity or while
they visit our campus or your departmental website.
sending unsolicited email is unavoidable, and in doing so
without subjecting the University to any possible legal
liability or ill-publicity, include a means in the email
either to invite the recipient to join your mailing list
or allow recipients to remove their email addresses from
your mailing list (e.g. through clicking an URL). These
removal requests should be dealt with in a timely manner.
In general, an opt-in approach is preferred to an opt-out.
attaching any file in mass mailings especially with the
unsolicited email (e.g. putting the file on the web site
for downloading can be an alternative).
direct attachment is unavoidable, keep it small by selecting
the most appropriate way (e.g. for image file, keep the
resolution to a reasonable level) and format (e.g. produce
an electronic document in pdf format instead of image format)
to generate the attachment file. Do not attach any file
that has embedded scripts, macros or requires any software
(including those plug-ins for browser) to execute as it
may impose unnecessary security risks to the recipients
and will likely be removed by the email server at the recipients'
watch out for the following upcoming laws related to the spam
email and make timely changes to the respective business operations:
bill set for LegCo
Council Brief Unsolicited Electronic Message Bill
technical assistance or advice be needed, please call our
CSC Help Desk at 2788 7658.