is it possible to play voice message by iaxmodem and hylafax before sending fax? Like "recieve fax please"
No, it's not currently possible with iaxmodem 0.3.1. Voice features will need to be added. Look for this in a future release, but not immediately.
is it really possible in asterisk to announce a message before call i call? can you please send a link where can i read about it?
It is possible, yes, but I've never done it. The process would involve some AGI scripting, most likely, where the iaxmodem's call would trigger another call with the voice message, and then the calls would get merged. It would be a bit tricky, but certainly possible.
IAXmodem will support voice eventually... it just doesn't right now.
Now there is such opportunity?
No, although you could conceivably do this with Asterisk's dialplan features independent from iaxmodem.
It's something that would be possible in iaxmodem, but it's just not on my priority list right now.
If it's really a feature that you want in iaxmodem soon, and if you're willing to pay for the development time, then I can prioritize it.