[CentOS] Re: slow SMTP-AUTH

Ray Van Dolson rvandolson at esri.com
Wed Jul 25 23:39:48 UTC 2007


On Wed, Jul 25, 2007 at 07:35:58PM -0400, Ugo Bellavance wrote:
> Ugo Bellavance wrote:
> >Brett Schroeder wrote:
> >>Ugo Bellavance wrote:
> >>>Hi,
> >>>
> >>>    I installed sendmail on a centos-4 openvz VM.  I set up SMTP-AUTH
> >>>and when I try to send mail using this server, there is a big delay in
> >>>which my e-mail client (Mozilla Thunderbird) just hangs.  The server, on
> >>>the other hand, is idle at the same time.  It does that no matter if I
> >>>use no encryption, TLS, or SSL.  When the client is 'hung' sendmail, on
> >>>the server side haven't logged anything yet for this connection.
> >>>
> >>>Any idea?
> >>
> >>Since nothing is logged on the server, it sounds like there is a 
> >>firewall (or
> >>other networking problem) in the way. You should use WireShark (or 
> >>tcpdump) on
> >>the client to capture the network traffic.
> 
> I disabled the firewall on the server, no luck.  I tried sniffing, I see 
> nothing weird.
> 
>   5.512292 74.59.221.180 -> 72.55.149.51 TCP 17274 > submission [PSH, 
> ACK] Seq=350 Ack=10923 Win=17461 Len=53
>   5.512984 72.55.149.51 -> 74.59.221.180 TCP submission > 17274 [PSH, 
> ACK] Seq=10923 Ack=403 Win=7504 Len=277
>   5.724172 74.59.221.180 -> 72.55.149.51 TCP 17274 > submission [ACK] 
> Seq=403 Ack=11200 Win=17184 Len=0
>  22.884013 74.59.221.180 -> 72.55.149.51 TCP 17274 > submission [PSH, 
> ACK] Seq=403 Ack=11200 Win=17184 Len=53
>  22.884918 72.55.149.51 -> 74.59.221.180 TCP submission > 17274 [PSH, 
> ACK] Seq=11200 Ack=456 Win=7504 Len=85
>  22.970714 74.59.221.180 -> 72.55.149.51 TLSv1 Application Data
>  22.971120 72.55.149.51 -> 74.59.221.180 TLSv1 Application Data
> 

Can you run strace on sendmail during a connection and see what it's
doing?  DNS is often the culprit when delays are concerned, so look for
anything along those lines.

Ray



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