I have a sendmail server and clients in the network connecting to it through Outlook Express. Clients can receive their emails, and can also send simple text emails. But when they are trying to send emails with atachments (no matter of the size for the attachement), or bigger text emails, the following error occurs (in Outlook Express):

"The connection to the server has failed. Account:'192.168.0.254',Server: mail.halashoppingcenter.ro',Protocol:SMTP, Port:25, Secure(SSL):No, Socket Error:10061, Error Number: 0x800CCC0E".

But when i am in pine, i can send any kind of email (with or without attachements... it works.
I also tried to connect via telnet on ports 110 and 25 and the connections succeeded in both cases.
I thought it might be a problem with the firewall, so i have disabled it in rc.local and the situation is the same.

I have to mention that this error appeared out of the blue, the sendmail server have been running for almost 1 year with no problems and such.
My question is: Is this a sendmail or an Outlook problem? And how can i solve it?

Thanks for any help.

Have there been any changes to the mail system recently? Upgrades of sendmail or outlook, configuration changes etc..?

What's your free storage space look like? (df -h)

The firm i am working for is moving its office from a location to another these days. But the mail system has remained the same. And the network topology is the same (we only added one switch).

Filesystem Size Used Avail Use% Mounted on
/dev/hda3 3.5G 1.6G 1.7G 48% /
/dev/hda1 197M 8.2M 179M 5% /boot
/dev/hdc2 2.0G 167M 1.7G 9% /home
none 62M 0 61M 0% /dev/shm
/dev/hdc1 2.0G 1.2G 782M 60% /var