Question

"connection to the server was interrupted"

Exchange 2007, Forefront Client Security, Exchange error messages

hi,
I have exchange 2007 SP1 enterprise edition on HP DL 380 G5 server with 4 GB RAM.
installed antispam agents and microsofoft forefront security for exchange 2007 SP1.
configured everything right as per the book.
my main problem that mu clients are using POP3/SMTP accounts over GPRS connection.
the problem is when I send mail larger than 700 Kb it takes like for ever and then in the end it gives the error >> "connection to the server was interrupted"
I experience the same situation if I'm using ADSl connection but for mails larger than 15 MB.
I reviewed everything and everything seems well. I have 1 MB 1:1 SDSL connection for the server
any recommendation???

i found that switching to port 578 that is already created in exchange.
it will perform bestter because ISPs maybe blocking port 25 even if it's secure.
i will love to hear more suggestions....