I have contacted my server, Optus Australia and they are unable to gain "Remote Access " to check any problems as there appears to be a block somewhere by Mozilla.

I have two desktops connected to the same server. (Optus / Australia) One PC that uses Incredimail as it's email access receives all the incoming e-mails. The second PC that uses Mozilla Thunderbird for it's e-mail access only receives 10% of the incoming mail. I have contacted my server, Optus Australia and they are unable to gain "Remote Access " to check any problems as there appears to be a block somewhere by Mozilla.