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POP3-SSL connection problems - firewall drops packets

fiede
Hello,

since two weeks we have some problems with fetching the mails from our pop3 accounts.

We have a exchange server and use "POPCon" to fetch the mails. Since two weeks POPCon generates failure messages that port 995 is unreachable. This stays for some hours till the problem resolves itself. This happens every two days but sometimes even twice a day... 

If we notice the problem, I stop the POPCon service and then have to wait for some minutes before I can start it again. Fetching the mails will then work again. If I start the service immideatly the problem stays.

After I did some troubleshooting I made a network log with whireshark. Only then I got the clue, that I should take a look at the firewall logs because the whireshark logs stated there came no server-HELLO after the client-HELLO from our server.

So I did indeed find that some packets were dropped during that time. 

2012:12:11-11:09:50 astaro-1904 ulogd[5592]: id="2001" severity="info" sys="SecureNet" sub="packetfilter" name="Packet dropped" action="drop" fwrule="60001" initf="eth7" mark="0x1000" srcmac="***" dstmac="yyy" srcip="mail-provider-IP" dstip="gateway-IP" proto="6" length="1492" tos="0x00" prec="0x00" ttl="58" srcport="995" dstport="12340" tcpflags="ACK"

2012:12:11-11:10:42 astaro-1904 ulogd[5592]: id="2001" severity="info" sys="SecureNet" sub="packetfilter" name="Packet dropped" action="drop" fwrule="60001" initf="eth7" srcmac="***" dstmac="yyy" srcip="mail-provider-IP" dstip="gateway-IP" proto="6" length="40" tos="0x00" prec="0x00" ttl="58" srcport="995" dstport="12365" tcpflags="ACK FIN" 


There are many dropped "ACK FIN" packets, but only one "ACK" packet.

What could be the problem?

Thank you for your help.


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Parents Reply Children
  • 0 in reply to BAlfson
    Hi BAlfson!

    I did speak with the mail provider.

    They claim to not have any problems (of course). They told me, their logs are clean of any connection failures.

    If our server is sending packets and the mail provider server is responding, why should the ASG think the connection is dead anyway?

    Also, why should it work most of the time but suddenly it stops for some hours and then it's working again? And if I stop the POPCon service for some minutes it then starts working immediately after starting the service. It makes all no sense to me.

    BTW - Restarting and upgrading the firmware of the ASG to the latest v8-release didn't do anything either.

    Thanks for any help.