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Most of the times when we send out a newsletter (around 30 kb) to our mailing list of 20,000 emails the server hangs up.

We use Mailenable to send out emails. The hosting provider has the following comments.

Our question is: Is there any particular setting on server or mailenable which will help this issue?

How do we put a throttling in mailenable if this is the best way?

From what I can tell is it looks like your email script that runs under your domains in IIS is performing something similar to a DOS to itself. At shortly before 11AM server time the number of connections made for this domain in IIS it starts rapidly climbing from about 150 to over 1000 by 11:30 server time.

At this time we really need to recommend that you redesign the mailing script so that it limits the number that it attempts to push. What I believe is occurring is it is opening numerous ports eventually consuming all the available connections on the server rendering it unresponsive.

There aren't many things that we can adjust to correct this as the script needs to have throttling put in place to prevent it form overloading the server.


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Assuming that you use the SMTP host in IIS you have to throttle in the app because there is no way to do this in IIS. Your server is hanging up because it is trying to send 20K emails at once ,which would lockup up most servers. Also sending that amount of email will likely get you on a spam list quite fast anyway.

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Thank you. This is very useful analysis. Are there any ready to use throttling scripts which are compatible with windows server and mailenable software? – N.V May 11 '12 at 23:59

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