[Dovecot] A question of imap timeout exit

[刘莹莹]

hello:
    I have a question on imap process:
   if a client connect to dovecot like foxmail(version 10) , dovecot  will start at least 3 imap processes , and these imap processes will online until client logout , if the client not logout ,the imap process will always online.  this is similar to the long connection  and  imap's auto logout timer is not effect in this case.
   now I have two questions:
1: if there are a large number of users online at the same time ( eg about 30 000 users): so dovecot should shart at least 30 000 * 3 imap processes,  if user not logout ,so many processes are online all the time .this is terrible.  I dot'n know if there is a solution ??
now I have changed the timeout = 2min and test ,dovecot active disconnected imap process ,but I don't think this is a appropriate option.
 
2: I want to know why auto logout timer duration of IMAP protocol must be not less than 30 minuters ??
 
My English is not vary good ,I'm sorry but I really want to know the answer .
thanks