Andreas,

> Does anyone know an alternative to the SMTPClient from the Network-Protocols
> package?

Not knowing what problems you have with it, I don't know if my answer
will be sufficient:

We run the exim MTA (mail transfer agent) on our servers. SMTPClient
then connects to localhost and sends all email there. No latency, no
connectivity issues and queue management becomes exim's problem.

Problems with SMTPClient and debugging then becomes localised to the
interaction between SMTPClient and the exim running on localhost.

-- 
Danie Roux *shuffle* Adore Unix - http://danieroux.com