The message XFMail.050123204801.Ted.Harding@nessie.mcc.ac.uk from (Ted Harding) Ted.Harding@nessie.mcc.ac.uk contains these words:
Any comments from people who are already familiar with Onspeed would be welcome.
You only get the speed with compressible items. Files like jpegs are only speeded up if you set the quality to low.
With the software I use, there's little to be gained as all mail/news sent and received is in compressed packets.
It is reported to speed up web browsing, but again - only if you're prepared to put up with low resolution pics.