colosanti
Somewhere you would have double forwarding configured.
Did you inadvertantly include everyone group in the groupnameall group ?
Check the headers of both emails received, they should show you the delivery path of each email and allow you to see why/where the second one is coming from.
The everyone@domain.com is only usable for local users ie on the LAN or connected via VPN. External users cannot send to this.
Re updating your server from 7.5.x
All the sme7 repos are moved to the obsoleted tree or defunct (closed). It is possible to use yum to update, but quite tricky as repos have to be set up in a non standard way.
The easiest way is to download the sme server 7.6 CD iso, burn a bootable CD & upgrade your server from CD. Look in the obsoleted iso tree of mirrors, see for 32 bit iso
http://mirror.canada.pialasse.com/releases/obsolete/7.6/iso/i386/ It is recommended that any sme7.x server be upgraded to the final release of sme7.6 before upgrading to sme8.x.
Then you can use a similar approach to update to sme8.0 or sme8.1 ie via disk, but I think you may have to burn the v8.1 iso image file to a DVD due to size constraints. Please check the update pages accessible from the main Wiki page. You can also use yum for that upgrade but you need to follow instructions carefully.
I think the sme8.0 iso will fit on a CD, but then you will have a few hundred Mb of updates to download when doing a yum update to sme8.1 (not a problem really on unlimited ADSL2+ etc).
Updates to sme9.0 can then ONLY be done by performing a full backup on sme8.1 & restoring that on a newly installed sme9.0 OS. There is no direct upgrade path, due to limits imposed by CentOS.
During all these updates your data & configuration & users etc should remain intact, but always do a full backup to USB before each major upgrade.