IT'S BACK!
I had this problem months ago without finding a cause but spending $150
modem-phone call & house call. I did find a workaround, create a new
identity, but its a big hassle Moving messages rules, etc.
I have a fast system with 1GB mem and about 30GB free on HD. routinely keep
it clean with Spy-bot and others as well as defraging and such.
Problem: when I send email of over about 200k it doesn't get out. I get
error that there was a system delay or other cause that caused my ISP to
drop the xfer