Re: sendmail Broken Pipe Error

From: John-Mark Gurney <jmg_at_funkthat.com>
Date: Wed, 26 Mar 2014 09:37:46 -0700
Gregory Shapiro wrote this message on Wed, Mar 26, 2014 at 09:23 -0700:
> > > 11:57:56.539788 IP MyServer.com.41115 > Smarthost.com.smtp: Flags [S], seq 1001452351, win 65535, options [mss 1448,nop,wscale 6,sackOK,TS val 407239960 ecr 0], length 0
> > > 11:57:56.555262 IP Smarthost.com.smtp > MyServer.com.41115: Flags [S.], seq 1277075046, ack 1001452352, win 8192, options [mss 1452], length 0
> > 
> > It should look something like:
> > 09:18:34.723280 IP jmgmac.funkthat.com.64724 > h2.funkthat.com.ssh: Flags [.], ack 177, win 33280, options [nop,nop,TS val 1854905469 ecr 3482476972], length 0
> >         0x0000:  4510 0034 d7ac 4000 4006 e1af c0a8 0003  E..4.._at_._at_.......
> >         0x0010:  c0a8 0004 fcd4 0016 7e48 238e d872 43dc  ........~H#..rC.
> >         0x0020:  8010 8200 7c08 0000 0101 080a 6e8f 9c7d  ....|.......n..}
> >         0x0030:  cf92 61ac                                ..a.
> > 
> > Notice the hex output...  I didn't see any of that in your output...
> > The last packet I was talking about is the last one that had length
> > 1448 that your server sent...
> 
> Willy mentioned that this only happened on mail with attachments.  Could it be an MTU issue?  Specifically, see:
> 
> http://www.sendmail.com/sm/open_source/tips/path_mtu/

I don't see how it could be...  If it is litterally only mail with
attachments and not large emails w/o attachments, then it's definately
not that issue..    He could just disable path_mtu on the server:
sysctl net.inet.tcp.path_mtu_discovery=0

to test this, but I'd be surprised if it allows email through, since
he's already getting 1448 byte packets through and acked before the
hang up occurs...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."
Received on Wed Mar 26 2014 - 15:37:48 UTC

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