Question: encrypt/decrypt with plugin mail_filter

[Zhang Huangbin]

Dear all,

I'm trying to encrypt/decrypt mail body with Dovecot plugin 'mail_filter':
http://wiki2.dovecot.org/Plugins/MailFilter

I wrote a Python script to read mail body and encrypt it, the encryption/decryption part is working as expected, but Dovecot always fail to write modified email on disk:

Error: Cached message size smaller than expected (1575 < 1644)
Error: Maildir filename has wrong S value, renamed the file from /var/vmail/domain.com/user/cur/1458165453.M632521P17600.c7.iredmail.org,S=1575:2, to /var/vmail/domain.com/user/cur/1458165453.M632521P17600.c7.iredmail.org,S=1575:2,
Error: Corrupted index cache file /var/vmail/domain.com/user/dovecot.index.cache: Broken physical size for mail UID 4
Error: read() failed: Invalid argument (uid=4)

I know this behave is clearly explained in Dovecot wiki page, the question is, is there any way to overcome this and let Dovecot correctly handle the encrypted/decrypted mail?

Thanks. :)