mass mailing - best practise

Good morning,

what  is the best practise in sending mass mailing to over 600k users? I
can only make static list, I can not  associate  this  group  of   users
into  dynamic  lists.  Static  mailing  list will not be a good solution
so deliver on the backend  is the only way to do it right?

PS. 
Sun Java(tm) System Messaging Server 6.3-4.01 (built Aug  3 2007; 32bit)
libimta.so 6.3-4.01 (built 17:13:29, Aug  3 2007; 32bit)
SunOS ophaniel 5.10 Generic_120011-14 sun4v sparc
SUNW,SPARC-Enterprise-T2000

Best regards,
Ernest Wypierowski