Hi, I started a tcpdump which shows a lot of TCP Retransmission from the sending server, while my server is always answering with an ACK:
--------------------------- 787 10404.027462 83.19.xx.xx 211.xx.xx.xx TCP orbix-locator > smtp [SYN] Seq=0 Win=65535 Len=0 MSS=1460 WS=5 788 10404.027481 211.xx.xx.xx 83.19.xx.xx TCP smtp > orbix-locator [SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0 MSS=1460 WS=6 789 10404.044224 83.19.xx.xx 211.xx.xx.xxTCP orbix- locator > smtp [ACK] Seq=1 Ack=1 Win=1048576 Len=0789 790 10407.046338 211.xx.xx.xx 83.19.xx.xx SMTP S: 220 mx.mydomain.de ESMTP MyDomain Mailer; Mon, 29 Aug 2011 16:31:31 +0200 (CET) 791 10407.063540 83.19.xx.xx 211.xx.xx.xx SMTP C: EHLO domino.senderdomain.de 792 10407.063556 211.xx.xx.xx 83.19.xx.xx TCP smtp > orbix-locator [ACK] Seq=88 Ack=24 Win=5888 Len=0 793 10407.063748 211.xx.xx.xx 83.19.xx.xx SMTP S: 250- mx.mydomain.de Hello domino.senderdomain.de [83.19.xx.xx], pleased to meet you | 250-ENHANCEDSTATUSCODES | 250-PIPELINING | 250-8BITMIME | 250-SIZE 41943040 | 250-ETRN | 250-AUTH DIGEST-MD5 CRAM-MD5 LOGIN PLAIN | 250-STARTTLS | 250-DELIVERBY | 250 HELP 794 10407.082584 83.19.xx.xx 211.xx.xx.xx SMTP C: MAIL FROM:<[email protected]> SIZE=125838 | RCPT TO:<[email protected]> | DATA 795 10407.086341 211.xx.xx.xx 83.19.xx.xx SMTP S: 250 2.1.0 <[email protected]>... Sender ok | 250 2.1.5 <[email protected]>... Recipient ok | 354 Enter mail, end with "." on a line by itself 796 10407.113082 83.19.xx.xx 211.xx.xx.xx SMTP [TCP Previous segment lost] C: DATA fragment, 1460 bytes 797 10407.113097 211.xx.xx.xx 83.19.xx.xx TCP [TCP Dup ACK 795#1] smtp > orbix-locator [ACK] Seq=485 Ack=112 Win=5888 Len=0 SLE=4206 SRE=5666 798 10408.929021 83.19.xx.xx 211.xx.xx.xx SMTP [TCP Retransmission] C: DATA fragment, 1460 bytes 799 10408.929036 211.xx.xx.xx 83.19.xx.xx TCP smtp > orbix-locator [ACK] Seq=485 Ack=1572 Win=8768 Len=0 SLE=4206 SRE=5666 800 10408.948966 83.19.xx.xx 211.xx.xx.xx SMTP [TCP Retransmission] C: DATA fragment, 1460 bytes 801 10408.948981 211.xx.xx.xx 83.19.xx.xx TCP smtp > orbix-locator [ACK] Seq=485 Ack=3032 Win=11712 Len=0 SLE=4206 SRE=5666 802 10408.951928 83.19.xx.xx 211.xx.xx.xx SMTP [TCP Retransmission] C: DATA fragment, 1460 bytes803 803 10408.951942 211.xx.xx.xx 83.19.xx.xx TCP smtp > orbix-locator [ACK] Seq=485 Ack=5666 Win=14656 Len=0 SLE=4206 804 10408.968860 83.19.xx.xx 211.xx.xx.xx SMTP [TCP Retransmission] C: DATA fragment, 1460 bytes [...] 987 12529.161226 83.19.xx.xx 211.xx.xx.xx TCP [TCP Previous segment lost] cesdinv > smtp [PSH, ACK] Seq=90632 Ack=485 Win=1048064 Len=0 988 12557.025842 83.19.xx.xx 211.xx.xx.xx SMTP [TCP Retransmission] C: DATA fragment, 1460 bytes 989 12557.025861 211.xx.xx.xx 83.19.xx.xx TCP smtp > gte-samp [ACK] Seq=485 Ack=128592 Win=64128 Len=0 990 12557.044861 83.19.xx.xx 211.xx.xx.xx IMF subject: [restricted] 991 12557.082295 211.xx.xx.xx 83.19.xx.xx TCP smtp > gte-samp [ACK] Seq=485 Ack=129238 Win=64128 Len=0 992 12557.186893 211.xx.xx.xx 83.19.xx.xx SMTP S: 451 4.3.2 Please try again later 993 12557.186905 211.xx.xx.xx 83.19.xx.xx TCP smtp > gte-samp [FIN, ACK] Seq=519 Ack=129238 Win=64128 Len=0 994 12557.203527 83.19.xx.xx 211.xx.xx.xx TCP gte-samp 995 12557.203656 83.19.xx.xx 211.xx.xx.xx TCP gte-samp 996 12640.632093 83.19.xx.xx 211.xx.xx.xx SMTP [TCP Retransmission] C: DATA fragment, 1460 bytes --------------------------- After 2.5 hours the email is transmitted completely (ending with an ".", checked by follow tcpstream in wireshard), but the sendmail or the milter ignore this and send a "reject=451 4.3.2 Please try again later". Why? It is strange that the sending servers needs up to 120 seconds to respond to an immediately ACK and answers with a Retransmission then. But even if the whole session takes 2.5 hours and I don't want to wait that long for such a small mail to be transmitted, I'd like to know which parameter/option is responsible for the timeout on my side. And is this just a strange network problem (MTU, firefall on sending side) or possibly my problem (as I sayed never seen such an error sind 2000K mails running through this system and only caused by this single server). Ciao Marcus _______________________________________________ NOTE: If there is a disclaimer or other legal boilerplate in the above message, it is NULL AND VOID. You may ignore it. Visit http://www.mimedefang.org and http://www.roaringpenguin.com MIMEDefang mailing list [email protected] http://lists.roaringpenguin.com/mailman/listinfo/mimedefang
