[CentOS] exim localhost vs 127.0.0.1

[Peter Eckel]

Hi Mihamina, 

> [mihamina at recette53 ~]$ rpm -aq | grep exim
> exim-4.72-4.el6.x86_64
> 
> [mihamina at recette53 ~]$ telnet localhost 25
> Trying ::1...
> Connected to localhost.
> Escape character is '^]'.
> 220 recette53.ideoneov.com ESMTP Exim 4.72 Mon, 11 Mar 2013 10:09:27 +0100
> HELO mihamina
> 250 recette53.ideoneov.com Hello localhost [::1]
> MAIL from: <mrakotom at free.fr>
> 250 OK
> RCPT to: <mihamina at rktmb.org>
> 550 relay not permitted
> 
> 
> mihamina at recette53 ~]$ telnet 127.0.0.1 25
> Trying 127.0.0.1...
> Connected to 127.0.0.1.
> Escape character is '^]'.
> 220 recette53.ideoneov.com ESMTP Exim 4.72 Mon, 11 Mar 2013 10:10:26 +0100
> HELO mihamina
> 250 recette53.ideoneov.com Hello localhost [127.0.0.1]
> MAIL from: <mrakotom at free.fr>
> 250 OK
> RCPT to: <mihamina at rktmb.org>
> 250 Accepted
> DATA
> 354 Enter message, ending with "." on a line by itself
> From: <mrakotom at free.fr>
> To: <mihamina at rktmb.org>
> Subject: Haftra Andrana

I'm not a specialist on EXIM, but obviously your system resolves 'localhost' to the IPv6 address ::1. 

Probably you have allowed EXIM to relay for 127.0.0.1/8, but not for ::1, so it will allow relay access on IPv4 localhost, but not on IPv6 localhost. 

Cheers, 

  Peter.