Help → Could not get a STATUS for any IMAP folder

Could not get a STATUS for any IMAP folder

following is what console output:
POPFile Engine v1.1.3 running
2019/1/4 19:47:17 21409: Warning: POPFile may require Perl module BerkeleyDB; it is needed only for "Upgrades from v0.20.x".
2019/1/4 19:47:17 21409: Warning: POPFile may require Perl module File::Glob::Windows; it is needed only for "Japanese Language Support (Windows only)".
2019/1/4 19:47:17 21409: Warning: POPFile may require Perl module MeCab?; it is needed only for "Japanese Language Support".
2019/1/4 19:47:17 21409: Warning: POPFile may require Perl module Text::Kakasi; it is needed only for "Japanese Language Support".
2019/1/4 19:47:17 21409: POPFile successfully started
2019/1/4 19:47:17 21409: IMAP-Client: 171: Connected to mail.ustc.edu.cn:143 timeout 60
2019/1/4 19:47:17 21409: IMAP-Client: 268: Could not get UIDNEXT STATUS for folder Sent.
2019/1/4 19:47:17 21409: imap: 441: Could not STATUS folder Sent.
2019/1/4 19:47:17 21409: imap: 272: Could not get a STATUS for IMAP folder Sent (Services/IMAP.pm(443))
2019/1/4 19:47:37 21409: IMAP-Client: 171: Connected to mail.ustc.edu.cn:143 timeout 60
2019/1/4 19:47:37 21409: IMAP-Client: 268: Could not get UIDNEXT STATUS for folder Sent.
2019/1/4 19:47:37 21409: imap: 441: Could not STATUS folder Sent.

Infact, I can't get e-mails in any folder. But I can refresh list of folders.