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ipchains help

Posted on 2002-06-12
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Last Modified: 2013-12-16
I recently configured sendmail and qpopper(pop3 server) on my Red Hat 7.2 machine.  Both those services seem to work correctly.  I only have trouble when I try to send email from that machine with the firewall up.  Receiving mail with the firewall up works fine though.  When the firewall is down though, both work correctly.  It is an ipchains firewall.

I would like to temporarily allow all traffic through the affected ports.  I have tried to do this using the following rules, but I have not succeeded.  Like I said, sending email while the firewall is up is not working.

As far a I know, this should allow the traffic that I need to go through.  Is there something I am missing that is not letting my attempts to send email from this box go through??

If these rules are correct, then there must be some other rule blocking my outgoing email traffic.  If that is the case, I don't know where to start in order to find the rule that is blocking my outbound email.  Any help would be greatly appreciated.(I'm pulling my hair out on this one!)  Thanks.


#PORT 53
ipchains -A output -s 0/0    -d 0/0 53 -p tcp -j ACCEPT
ipchains -A input  -s 0/0 53 -d 0/0    -p tcp -j ACCEPT
ipchains -A input  -s 0/0 53 -d 0/0    -p udp -j ACCEPT
ipchains -A output -s 0/0    -d 0/0 53 -p udp -j ACCEPT

#PORT 110
ipchains -A output -s 0/0 110 -d 0/0     -p tcp -j ACCEPT
ipchains -A input  -s 0/0     -d 0/0 110 -p tcp -j ACCEPT

#PORT 25
ipchains -A output -s 0/0 25 -d 0/0    -p tcp -j ACCEPT
ipchains -A input  -s 0/0    -d 0/0 25 -p tcp -j ACCEPT
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Question by:barthalamu
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by:wqclatre
Comment Utility
try to add
ipchains -A input -p tcp ! -y -s 0/0 25 1024:65535 -j ACCEPT

to allow reply from the reciving mailservers.
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wqclatre earned 250 total points
Comment Utility
sorry missed one thing.

ipchains -A input -p tcp ! -y -s 0/0 25  -d ip_of_mailserver 1024:65535 -j ACCEPT

should it be.

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by:barthalamu
Comment Utility
Well, that didn't work...but it got me going on the right track.  I ended up making both of my SMPT bidirectional, (with the -b parameter) and that worked.  Thanks a lot for your help.
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