unable to send a 800kb zip file

My system is a ibm cyrix 233 with 128mb memory using windows 98se, microsoft IE ver 6 and OE ver 6.

Just a couple of day ago, I could send a zipped file from my outlook express. Today I am unable to send the same file to someone else. Outlook express message says that the mail could not be sent due to the limitation of the server size. I have nothing else in the server. I checked with my ISP and they confirmed me that there is enough capacity in my box.

It also advised me to select the process of sending by splitting the file by selecting that option in tools/accounts/properties/advanced to break the messages into smaller parts.

After choosing this option, message reads that it is unable to break the file in to small parts.

What could be the problem? can you pleas help