Legacy versions do not receive the latest security patches. If you use Zoiper over public networks without a VPN, you could expose your system to vulnerabilities.
Which (like Asterisk or FreePBX) are you connecting to? Zoiper 3.15 Download--
Features a wide array of voice codecs including a-law, U-law, GSM, Speex, and G. 729 (available as a paid upgrade). Why Users Still Search for Zoiper 3.15 Legacy versions do not receive the latest security patches
Zoiper implements to protect your communications: Zoiper 3.15 Download--