Hallo there! My first post in here!

I am a junior Systems Admin with one year of experience, (I was thinking about starting from MCITP Win Server 2008 sys admin, what do you think?)
I am the only IT guy in a small company in Greece wich runs Win Server 2003 Domain and Exchange 2007.
For the previous weeks I was experiencing problems sending to yahoo, after a long search I found out that I had to change the Send connector's name to fix the problem but it was not the only one I had to do..
I realized that in the event viewer I continiously take this
error unfortunatelly I do not have an account to eventID in order to view the solution. Through google I tried to study some articles from microsoft but it wasn't easy to solve the problem through the exchange's command sell.
I got confused!

I have also found
this in order to troubleshoot the problem.. I think that I have to create a certificate that corresponds to the Sent connector but with the right domain name: mail.company.gr but how I will do it? What is the command I should type exactly and after that how I will enable the new certificate?
Can someone help me in order to edit the certificates FQDN name or how to create a new certificate with the right name of my exchange server in the Send connector?
Thanks in advance, sorry if this is not the right place to post my problem..
Lefteris