Subject UTF-8 encoded when reply to message

[LouisvL]

Hi

My domain hoster mailserver regularly sends me aan email with an overview of spam held on the server.
When replying the subjectline tells the spambot which emails to release.
This subject is in the form
/m/myname32/14376(someIDnumber)/somecharacters

Since yesterday I use a Synology Diskstation with Roundcube. I cannot get the spambot to release emails it withheld.
After a long search I found out the subjectline is UFT-8 encoded, like
?UTF-8?Q?/m/myname=33=32/=31=34=33=37=36(someIDnumber)/(somemorecharacters)
the spambot does not recognise this subjectline and doesn't give any reaction.

Can I somehow prevent roundcube from utf-8-encoding the subjectline?

Thans all for your reaction
:-)