I have a Performa 1800(OS 8.6)and a 28.8 internal modem which would occasionally be used to check e-mail. I cannot connect to my ISP(Concentric). I am unable to connect to the server. Concentric tech support which is usually very good said that they can give me the connect commands but they don't know where the files are on a MAC. I have not had any luck looking for a user modifiable modem file.
When using the modem as a fax it work fine and my other Macs with faster modems work also work well.