Hello,
Use the following syntax:
exten => 100,1,SIPAddHeader(Call-Info:<sip:>\;answer-after=5)
exten => 100,n,Dial(Sip/mynumber)
Note, you can change the ";answer-after=value" option to the desired value in seconds. The example above is set for auto-answer after 5 seconds.
You can enable the option in Zoiper5 under:
1. Open the Zoiper Options window;
2. Automation
3. Enable the "Accept server-side auto answer" option.
Note, this is supported only for SIP.