Since 1.33v we have leave a message functionality. It ads another type of functionality then there is no online operators. By default app allows to write messages for users then there is no online operators, it writes to user that he can leave a message. Now instead of that window you can show window leave a message window then there is no online operators. To enable this window you just have in html code generation window check
And after that user will see request form. You can also edit template in e-mail templates section.
Developing application takes a lot of time. You can support application by donating. There is no company behind this application and it takes away my free time. Every donation matters and does not matter how small it is!