Zoiper

Zoiper is a free softphone for making VoIP calls, available for many platforms. The program supports both SIP and IAX protocols. It allows you to exchange instant messages, make video calls, send and receive faxes, see the presence status of your contacts, and so on. The program is well suited for both simple communication and business. The paid Pro version adds encrypted calls with TLS, SRTP and ZRTP.

The free version is intended for non-commercial use, and the Pro version adds call transfer, conferencing, contacts integration with Outlook and LDAP, browser click-to-dial and the G.729 and H.264 codecs. The program works in the following way: at the first start Zoiper asks for the username and password of an existing VoIP account from your provider or from the office IP PBX and tries to find the configuration automatically. You can also pick a provider from a built-in list that can be searched by name, country or IP address. After that you will see all the functionality of this application. In the settings you can configure your SIP and IAX accounts. When you call, you get a high quality picture, but in order to save traffic, or because of the lack of speed, the video quality can be reduced in the settings. You can also set up everything related to sound, contact list, chat. The status menu lets you appear as Online, Invisible, Away, Busy, Offline, Out to lunch, On the phone or Be right back.

Zoiper offers versatile communication options including video calls, instant messaging and fax, making it ideal for personal or business use.