can't send or recive any emails

[tamer amr]

thank you for your concerning 
  and i really approcitiate that  and i want to tell you something i am trying to be a powerful administrator so i get some mistakes please forgive me and help me to get the right configurations 
  by the was what is the wrong in the forward chain ? and the output chain 
   
  thank you 

Lord of Gore <lordofgore at logsoftgrup.ro> wrote:
  First of all I want to say that *I know* that the problem is solved but 
I see the same mistake done over and over again and I hate this.
For anyone having problems. You should post *consistent* and *correct* 
info about your problem. Otherwise your post could sound like this:
"Hello, I have a service that is not working. What is the problem?"

Here is how I interpret your mail:

tamer amr wrote:
> when i send an e-mail form yahoo or my mail server i get this error 
> 
> Remote host said: 550 5.0.0 Access denied
> what is the problem ?
> 
What mail server said this? Yours or another? From whom did the mail 
originated and was addressed to whom?
> this is my configurtion for my iptables firewall
> 
I believe that your iptables rules are a bit messed up...
> Chain INPUT (policy ACCEPT)
> 
policy for input chain is ACCEPT all packets
> target prot opt source destination
> DROP all -- 0.0.0.0/0 0.0.0.0/0 state INVALID
> ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state NEW
> 
here you accept all packets that do not correspond to any established 
communication? Why? This includes packets that start a new connection.
> ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
> 
this should be ok if you'd have DROP policy on the INPUT chain but as 
you have ACCEPT policy it doesn't make any sense.
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:80
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:143
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:53
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:67
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:443
> 
All this is useless given the fact that you have ACCEPT policy. All 
these are already accepted.
This config would make sense if you would have DROP policy on INPUT 
chain and you'd erase the NEW state rule. Then you would have opened 
only http, imap, domain, 67??? (maybe you moved ssh to this port...) and 
https. Then you should experience problems on port 25 and as a response 
you'd "pierce" your firewall with a ACCEPT --dport 25 rule.
> LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG flags 0 level 4
> 
> Chain FORWARD (policy ACCEPT)
> target prot opt source destination
> ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
> ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
> 
Useless given the policy on FW chain...
> 
> Chain OUTPUT (policy ACCEPT)
> target prot opt source destination
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:67
> 
same 67 port, I wonder what you use it for...
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:53
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
> ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:80 state RELATED,ESTABLISHED
> 

Also useless for the same reason.

>From here I can draw only two conclusions either you sent another 
iptables config (maybe from another machine) or you should be wide open 
to incoming traffic.
So, having said that I wonder how this is resolved by unblocking 
something that wasn't blocked in the first place...
My belief is that:
You were trying to solve the problem on your own and modified all 
policies to accept to see if the firewall was the problem. Then you 
posted the modified config to the list. The next step was mr Waleed and 
mr Nilesh not reading the rules correctly and erroneously sending you to 
the answer to the problem. Well a few of you will say "What's your 
problem? The guy had it's problem solved!". Well I think that solving 
the problem by making two incorrect decisions would not benefit to 
anyone. This list's scope (from my point of view) is not about solving 
problems but mostly about evolution. I read threads that I find 
interesting and could teach me new stuff and I think so do others. And 
from those others a few might have not understood nothing from this 
thread although it's about basics on firewalling with iptables...
So, again: guys, if you have problems post as many info regarding the 
problem as you have and try not to post incorrect info.
Maybe this will be added to the etiquette of this list and it will be 
reminded to everyone that does not respect it.

Thank you for your patience,
LoG

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