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Old 04-11-2006, 04:05 PM   #1
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Is my issue with sendmail when sending to a large number of users?


We periodically send out email broadcasts to a large number of users. One of those broadcasts is being sent from a customized application written for our company and I am trying to determine if the speed of the broadcast is sendmail related or application related. The list of users was over 800 names and after 48 hours still had not completed. That seems extremely excessive even if it were a sendmail issue. That seems to indicate to me it is application-related.

I also was having a similar problem this morning using Microsoft Outlook. I pasted all of my recipients (I didn't count the number, but it was several hundred) into the BCC field of an email. I receive a server timeout sending the message. On the same system, I have no trouble sending a message to an individual.

I sent an email yesterday to all of my users (about 150) at my company using Thunderbird and had no trouble at all. It sent all of them in a couple of seconds.

So...

My question is basically this:

Is it possible that there is something in sendmail which is attempting to verify all recipient addresses in an email? I'd like to disable such checks on all outbound issue if it is my configuration that is causing this problem. It seems to me that it is possibly server-related if I have had a similar issue on multiple systems.
 
Old 04-13-2006, 01:25 PM   #2
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Is it possible that there is something in sendmail which is attempting to verify all recipient addresses in an email?
The MTA must find the mailhost for user@domain by looking up the MX record for the domain.


I'd like to disable such checks on all outbound
That approach does nothing to solve the root cause. Instead of trying to force email out you could check the address (or at least the mailhost) to send to is available by whatever means you have before submitting to the MTA. Next to that you could consider sending email in more batches with smaller amounts of addresses per email. This should spread the risk of a batch getting stuck for whatever reason and if one does you could test MX availability with something simple like (infile only contains "user@doma.in" formatted lines):
Code:
grep @ infile|cut -d "@" -f 2|sort|uniq|while read domain; do echo "/mx ${domain}"\
|echo "${mx}: $(sendmail -t -v -bt -Lsendmail_mxtest 2>&1)"; done|grep "returns.0"
The "grep "returns.0"" removes output for any domain that has an MX record. There's more reasons it can get stuck but apart from tuning .cf timeout variables there is, as far as I know, not much you can do about that.
 
Old 04-13-2006, 05:02 PM   #3
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Thanks, but...

I am working with a custom app which is sending out the emails. After some discussion with their programmers, the emails come from a list but are being sent individually so the issue is highly unlikely to be in sendmail.

But...the Outlook emails are an issue. I can request that my users send in smaller batches, but that's a user issue to try to deal with. They like to take reports from excel with a column of emails and grab every address to send out an email. This was never an issue with IMAIL, which was what we used to run. I set the timeout on the client side to 10 minutes for response from the SMTP server and the emails seem to go (though it takes time to process). It would make a whole lot more sense to just be able to send the emails out and let the remote domain (or absence thereof) send back any rejections. It makes little sense to me that my server should be verifying domain names before sending emails.
 
Old 04-24-2006, 02:24 PM   #4
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4 Minutes...

I am curious if there is a sendmail limitation which limits the ability of a specific account to send more that a certain number of messages with great speed.

I have tried this on two systems with identical results. Both systems will rapidly send about 24 messages then slow to a crawl, sending one message every 4 minutes.
 
  


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