Roundcube does not send read confirmation mail

[Raidu]

Hello!

I have a problem. My roundcube does not send read confirmation mail to outside of the local network. If you send a email to [email protected] <- local user as in using the roundcube in our network then it send the read confirmation mail, but if we send out a mail to someone else whos out of our network the confirmation mail does not come if the user has read the mail.
I need help

[SKaero]

Practically all email clients give the user the option not to send the read confirmation email so probably the users on the other end are just deciding not to send them.