I just tested the performance with a very simple program:
It takes... about 50(!) seconds to send this 50 mails! This for sure also depends on the mail-server (in this case it is an MSEX) and some other circumstances, but it indicates that it should be a really hard task to achieve your goal...
As you realize, I did not try anything to speed up the sending; for performance questions (and some other) have a look at
http://developer.java.sun.com/developer/community/chat/JavaLive/2000/jl1212.html (interview about JavaMail 1.2)
On the other hand, it is less a question of "another" mail-api but a question of the possible use of an other SMTP-provider (I used the SUN-implementation; but on
http://java.sun.com/products/javamail/Third_Party.html there is no other).
But: Have a look at
http://oss.software.ibm.com/developerworks/projects/smtp and try out, maybe this helps (even if I do not like do leave the sun-path...)
Hope it helps
Detlev
[This message has been edited by Detlev Beutner (edited July 20, 2001).]