Relocate subfolders to different mount point

[Marc Roos]

I would like to relocate the subfolders of the Sent folder to a 
different location. Now send messages mail is stored in mbox format at 
the location /home/users/testuser/mail/.Sent. 
I would like to store the subfolders Sent/2017 and Sent/2018 at the 
location /home/archive/users/testuser/.Sent.2017 and 
/home/archive/users/testuser/.Sent.2018

Is this even possible?

I am using currently using this mail_location:
mail_location = 
mbox:~/mail:INBOX=/var/spool/mail/%u:CONTROL=~/mail/control:INDEX=/var/d
ovecot/%u/index:LAYOUT=maildir++

/var/dovecot is on a ssd
/var/spool/mail is on sda
~/mail is on sdb with these folders

[@mail]# ls -ac1
.folderc
.Drafts
.foldera
control
.Trash.folderc
.folderb
.Sent
.Sent.2018
.Trash