Iax trunk or sip trunk?

hi ,
i want to send fax by hylafax client , i have sip trunk with provider , i want to send to to fax by trunk from provider.

the question is :
for fax

do i need iax trunk ??
or sip trunk ??

or whatever will work ???
with to help


I’ve used both IAX2 and SIP trunks for faxing but make sure that you stick with G.711a or G.711u throughout. Transcoding has a very bad effect of fax signalling.

FAX can be unreliable over IP anyway but I’ve personally not had major problems using modern fax machines or fax to e-mail.