295433Re: Connection Speed
- Sep 12, 2013you are right. The telnet connection from that machine was instantaneous.
On Thu, Sep 12, 2013 at 10:14 AM, Viktor Dukhovni
> On Thu, Sep 12, 2013 at 10:03:58AM -0400, Roman Gelfand wrote:
>> Based on comments made by Wietse, it looks like my server is in good
>> shape as the connections are not even taking a second and the whole
>> process is taking roughly a second.
> Whether that is slow or not depends on what throughput (messages
> sent per second) you're trying to achieve and what concurrency
> (number of parallel submission processes or threads) you're using
> to submit mail. Mail delivery is "congested" when the output rate
> is below the input rate, otherwise mail is inevitably delayed in
> transit by a short time, but that is rarely a concern.
>> Based on what Viktor is saying, this line could be a problem
>> Sep 12 09:39:56 pmx1 postfix/smtpd: connect from unknown[192.168.0.86]
>> as it could to take some to time to attempt resolve this dns. Is this
> A single log message with a single timestamp in isolation is NOT
> evidence of delay. All we see is that reverse resolution of
> [192.168.0.86] failed, whether this took any appreciable time is
> not evident from this log entry alone. There are often prior log
> entries warning about the resolution failure of DNS lookups timed
> out, ...
> To determine whether there is a delay, use "telnet" to connect from
> 192.168.0.86 to port 25 on the MTA, and see how long you have to wait
> until the MTA responds with a "220 ..." banner.
> You can also capture with "tcpdump" and see timestamps to the
> microsecond showing how long it takes from TCP SYN to "220 ..."
> (and what DNS lookups are taking time in between).
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