Messages not saved to my "Sent" folder

[Esteban L]

Hello, 

Using Dovecot 2.2.27

1. Had an issue where my Sent box, "disappeared." I used to be present,
but then it was just gone. I went in and changed the
/etc/dovecot/conf.d/15-mailboxes.conf

the auto=subscribe feature had disappeared, even though I had added
that line at setup. Below is the new changes.

# For \Sent mailboxes there are two widely used names. We'll mark both
of
  # them as \Sent. User typically deletes one of them if duplicates are
created.
  mailbox Sent {
    special_use = \Sent
    auto = subscribe
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
}

2. But, mail is STILL not sent to SENT folder.

3. I have reload both postfix and dovecot, and also systemctl restart
postfix && systemctl restart dovecot.

The Sent folder is present, but no mail is stored to it.

4. Before sending this email, I checked my mobile client, and the Sent
file was full from previously sent email. When I "updated it"/repolled
it, it is now empty. 

Any able to lend a helping hand?

Thanks.