安装 http://lnmp.org/install.html
yum -y install libc-client-devel
cd */ext/imap
/usr/local/php/bin/phpize
./configure --with-php-config=/usr/local/php/bin/php-config --with-kerberos --with-imap-ssl
make && make install
编辑 /usr/local/php/etc/php.ini 添加 extension=imap.so 重启 nginx 即可