So I would like to know how I can obtain one because the problem bothers a lot
Are you looking for the patch for smb3? The older firmware for the slow scanning? Your Subject implies the email issue, and thus you would want the firmware, but since it appears from your wording that the issue with the subject (slow email) was resolved, that the subject line is totally irrelevant to the actual issue scanning to SMB.
If its the SMB thing, you need to state what version of firmware you are running at the very least, but the actual patch name would be incredibly helpful too.