问题：dovecot并发数造成foxmail、outlook等客户端工具接收邮件有时候报错，关闭客户端工具后又可以了。
/var/log/maillog日志有大量的报错：
mail dovecot: imap(fasong@test.net): Error: Raw backtrace: /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(+0x698da) [0x7ff093ecd8da] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(+0x69946) [0x7ff093ecd946] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7ff093e8664d] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(+0x7ed81) [0x7ff093ee2d81] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(+0x7edbb) [0x7ff093ee2dbb] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(p_strdup+0x3e) [0x7ff093ef00ee] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(maildir_uidlist_refresh+0x7f0) [0x7ff09418b3f0] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(+0x53b19) [0x7ff09418ab19] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(maildir_uidlist_sync_init+0x4d) [0x7ff09418ba4d] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(+0x4f13d) [0x7ff09418613d] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(+0x4f673) [0x7ff094186673] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(maildir_storage_sync_init+0xd9) [0x7ff094186919] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(mailbox_sync_init+0x31)
[0x7ff0941b4561] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot-storage.so.0(mailbox_sync+0x27) [0x7ff0941b55e7] -> dovecot/imap(cmd_select_full+0x183) [0x4118d3] ->
dovecot/imap(command_exec+0x3d) [0x416fbd] -> dovecot/imap() [0x4160d0] -> dovecot/imap() [0x4161bd] -> dovecot/imap(client_handle_input+0x11d) [0x41643d] -> dovecot/imap(client_input+0x6f) [0x4167af] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(io_loop_call_io+0x4e) [0x7ff093eddbfe] -> /usr/local/kkmail/service/dovecot/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0xa7) [0x7ff093eded67] ->
/usr/local/kkmail/service/dovecot/lib/dovecot/lib
mail dovecot: imap(fasong@test.net): Fatal: master: service(imap): child 19713 returned error 83 (Out of memory (service imap { vsz_limit=256 MB }, you may need to increase it) - set CORE_OUTOFMEM=1 environment to get core dump)
解决：这是某个邮箱造成imap崩溃，提示不够内存。更改配置文件dovecot.conf(也可以改成0，改成0不接单位)
[root@gxm log]# vi /usr/local/kk-mail/config/dovecot/dovecot.conf
default_vsz_limit = 2048 M
service pop3 {
process_limit = 20480
vsz_limit = 2048 M
}
service imap {
process_limit = 20480
vsz_limit = 2048 M
}
[root@gxm log]# cd /usr/local/kk-mail/service/dovecot/bin/
[root@gxm bin]# ./doveconf | grep "vsz_limit"
default_vsz_limit = 2 G
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 2 G
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B
vsz_limit = 2 G
vsz_limit = 18446744073709551615 B
vsz_limit = 18446744073709551615 B重启dovecot服务。
