Have you guys ever encountered a phone system unable to pass through the DTMF digits to a fax server?

Perhaps, it may use a priority voicemail card and not be design to pass down those digits to any extensions?

I am not sure if any fax server companies has ever complied a list of compatible phone systems which are able to pass through DTMF digits. I think that most techs do not know offhand how to do this.

Have you ever setup a fax server of any Samsung phone system?

Thanks.