早上有人反應webmail打不開
查了一下log
發現如下的情況

Aug 26 09:44:09 mail dovecot: master: Warning: service(imap): process_limit reached, client connections are being dropped
Aug 26 09:45:20 mail dovecot: master: Warning: service(imap): process_limit reached, client connections are being dropped
Aug 26 09:46:25 mail dovecot: master: Warning: service(imap): process_limit reached, client connections are being dropped
Aug 26 09:49:32 mail dovecot: master: Warning: service(imap): process_limit reached, client connections are being dropped

imap 超過預設值了

修改/etc/dovecot/conf.d/10-master.conf
#default_process_limit = 100
default_process_limit = 2000
#default_client_limit = 1000
default_client_limit = 4003

service auth {
加上
client_limit=6048
}

dovecot restart後再觀察看看
dovecot restart時如果預設值有問題
會顯示應該調整的參數

升到centos 6 後不管是postfix或是dovecot 預設值都滿低的
只能夠碰到問題再來慢慢調整了