How does Spell Check functionality work in Zimbra server?

[Sbhingarkar]

Greetings,

I am trying to understand the behaviour of spell check functionality in Zimbra server.Based on my initial findings i could find following things:
1)Zimbra server uses GNU Aspell open source
2)This gets installed during zimbra server installation.
3)We need to specify some url for this service/server while installation.

Apart from this information ,I need to know:
1)Can we specify another spell check server ?
2)How does the response is received and understood by Zimbra server code?
3)Can GNU Aspell be installed as a separate server/service?Is it dependant on Tomcat or apache library?

If any pointers are provided to additional information about spell check facility
it will really help me to understand the functinality?

Thanking in advance.

Thanks
-Sudhir