IMAP mailbox names are encoded in a modified UTF-7 when names contains international characters outside of the printable ASCII range. The modified UTF-7 encoding is defined in RFC2060(section 5.1.3).
acquired package info from repodata DB: repodata/f1f85c23079e7764ad00378a9fc5d660b89a03657290e75426caf7be5b7da462-primary.sqlite.bz2