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43976 visitors since
September 1, 2000
Last Updated on
5 August 2005
by Hianoto Santoso
Copyright © 2002-2005
by Hianoto Santoso
How to Limit SMTP Size Properly
In your company, VIP users are allowed to send unlimited outgoing message size; however
for other ordinary users, you must set some limit for outgoing message size. To make it
more complex, for local mail sending, both VIP users and ordinary users can send whatever
messages with no size limitation. How to do that ??
Initially, the basic requirement was simple, I need to configure MDaemon to limit outgoing message size for all users, that's it. However, I did it wrongly *sigh*. Interestingly, there are many people do the same mistake or ask how to do it in the mailing list.
First attempt, I used the setting "Maximum acceptable SMTP message size" in Setup - Miscellaneous Options - Servers tab.
Figure 1: Maximum acceptable SMTP message size
It seemed correct, whenever I tried to send a message with attachment larger than the size specified, MDaemon rejected it properly. Then I was confidently applied the configuration to the Primary Mail Server. After monitoring the log, I found out that MDaemon rejected the incoming messages larger than the size specified. Yikes !! Finally I knew that the setting covered both incoming and outgoing messages, I thought Alt+N should highlight the impact of some 'dangerous' settings, either in the Online Help or the application itself.
The second attempt, I used the Content Filter to do the job. It was quite simple,
the steps were:
Figure 2: New Content Filter to limit SMTP Size
Figure 3: Send notification to sender along with the original message
Note:
Ordering is very important in determining the steps of actions taken in Content Filter.
If you tick "Delete the message" first, then tick "Send a note 1 to ...", the sender
will never receive a notification because the message is deleted already. Please ensure
the option ticking is done in order.
After checking the result, I reconsidered the configuration once again. I remembered the purpose of limiting outgoing messages size is to minimize the bandwidth usage. Thus local mail sending should not be limited. I made a small changes, to apply the Content Filter rule only to Remote Queue. I just reopened that Content Filter rule, then clicked the underlined blue link for "LOCAL & REMOTE", then unticked "Local Queue" and click Ok
Figure 4: Apply the rule for Remote Queue only
Now after the rule was applied, I had a lot of complains from VIP users, that they
could not send messages with some attachments. Then I made the forth attempt, by
allowing VIP users to send message with no limit. The steps were:
Note:
Since we configured to skip 1 rule if the messages were sent from VIP users, then
we had to put this rule prior to the rule to delete large messages. The failure
of doing this will make VIP users cannot send large messages.
Figure 5: Skip the rule for message from VIP Users
Figure 6: Specify the VIP Users List
Figure 7: Remember to specify "Any" to make "OR" logical connector to be used
Figure 8: Remember to use the proper order for both rules
Hopefully you can now limit the size of outgoing messages while keeping your VIP users satisfied of getting unlimited size :-)