[Exim] exim and pppd (via mobil-telephone)

Hello to all,

Curently I have no internet access at home and must download every
day around 3-4 MByte E-Mails in a Cyber-Center, put it onto Floppys
and pass it at home local to procmail (on my nfs-server).

At home I read the E-Mails, answer and next day I go to the Cyber-
Center to send the E-Mails... :-/

I like to deliver the E-mails in the night as fast as possibel and
economic.

Now I install on an old machine (486dx2/66) a Mailserver with exim.
so I send all mails from my Workstationd (Linux, Dos, BSD, Win) to
it.

But exim must spool the E-Mails and send it only all 2-3 hours OR
(!!!) if the spooler has more then 60 kByte in it...

This is, because I must pay 0.10 Euro (or US$) per minute...
...and my current access has only 9600 BpS (next time I get HSCSD
with 38400 BpS).

Can anyone help me precisly ?

I do not know, how to configure exim correctly to hold the messages
(it send the E-Mails immediatly to the Mobil-Telephone).

So exim is only a smtp-relay.

Thanks in advance
Michelle