I modify this file:
1)
/etc/psa-webmail/horde/horde/php.ini
upload_max_filesize = 128M
post_max_size = 128M
2)
/etc/psa-webmail/horde/imp/conf.php
$conf['compose']['attach_size_limit'] = 0;
3)
/etc/postfix/main.cf
mailbox_size_limit = 20480000
message_size_limit = 20480000...