In general, any SIP provider should work. If you want to share your provider settings, please contact the support.
FRITZ!Box
With FRITZ!Box, the typical setup is different. Instead of configuring Telephone directly with the SIP provider settings, these settings should be configured in the FRITZ!Box as an internet phone number. After that, an internal IP phone account should be created in the FRITZ!Box for Telephone and any other hardware or software phone. These internal phone settings are then configured in the app.
In FRITZ!Box:
Configure your external phone number. Models: 6490, 7170, 7390, 7490, 7580, 7590.
Create an IP phone account. Models: 6490, 7170, 7390, 7490, 7580, 7590.
In Telephone:
Domain: fritz.box
User Name: username of the created IP phone account
1und1
www.1und1.de
Domain: sip.1und1.de
User Name: 49123412345
STUN Server: stun.1und1.de
Callcentric
www.callcentric.com
Domain: callcentric.com
User Name: 17771234567
Reregister every 1800 seconds
Cheapnet
www.cheapnet.it
Domain: sip.cheapnet.it
User Name: 655xxxxxx
e-fon
www.upc.ch/de/business/e-fon/
Domain: e-fon.ch
User Name: e-fon username
Registry Server: sip01.e-fon.ch
STUN Server: stun.e-fon.ch
Use DNS SRV: Checked
easybell
www.easybell.de
Domain: sip.voipcs.de
STUN Server: stun.voipcs.de
Internetcalls
www.internetcalls.com
Domain: sip.internetcalls.com
User Name: Internetcalls username
STUN Server: stun.internetcalls.com
ippi
www.ippi.com
Domain: sip.ippi.com
Localphone
www.localphone.com
Domain: localphone.com
User Name: 1234567
Password: <SIP password>
Megafon Multifon
multifon.megafon.ru
Domain: multifon.ru
User Name: 792xxxxxxxx
Use DNS SRV: Checked
Nomado
nomado.eu
Domain: sip.nomado.eu
Nonoh
www.nonoh.net
Domain: sip.nonoh.net
STUN Server: stun.nonoh.net (optional)
Open VOIP
www.openvoip.it
Domain: sip.openvoip.it
phone.systems
phone.systems
Domain: 123.4567.sip.pbxww.com
User Name: 0x97EF7EEE
Peoplefone
www.peoplefone.ch
Domain: app1.peoplefone.ch
SAPO
www.sapo.pt
Domain: voip.sapo.pt
User Name: +351<VoIP number>
Password: <VoIP account password>
SIP Address: +351<VoIP number>@voip.sapo.pt
Connect using proxy: checked
Server: proxy.voip.sapo.pt
Port: 5070
Sipcall
www.sipcall.ch
Domain: sip.backbone.ch
Sipgate DE
www.sipgate.de
Domain: sipgate.de
User Name: 1234567e0
Sipgate UK
www.sipgate.co.uk
Domain: sipgate.co.uk
User Name: 1234567e0
sipload
sipload.de
Domain: sip.sipload.com
User Name: sip12345
STUN Server: stun1.sipload.com
Sipnet
www.sipnet.ru
Domain: sipnet.ru
STUN Server: stun.sipnet.ru
Swisscom
www.swisscom.ch
Domain: 192.168.1.1 (router address)
User Name: <authentication user name>
SIP Address: 220@192.168.1.1 (<internal phone number>@<domain>)
Telekom new
www.t-online.de
Full Name: +49123xxxx (phone number)
Domain: tel.t-online.de
User Name: username@t-online.de (Kundencenter username)
Password: <Kundencenter password>
SIP Address: +49123xxxx@tel.t-online.de
Use DNS SRV: Checked
Telekom old
www.t-online.de
Full Name: 0123xxxx (phone number)
Domain: tel.t-online.de
User Name: 0123xxxx (phone number)
Password: <Kundencenter password>
Use DNS SRV: Checked
Vbuzzer
www.vbuzzer.com
Domain: vbuzzer.com
ViaTalk
www.viatalk.com
Domain: shockwave.vtnoc.net
User Name: 12345678901
Viva
www.viva.gr
Domain: viva.gr
User Name: 30xxxxxxxxxx
Vodafone Iceland
vodafone.is
Domain: sip.vodafone.is
User Name: phone number
Vodafone Deutschland
www.vodafone.de
Domain: sip.kabelfon.vodafone.de
User Name: 123456789
SIP Address: +491234567890@sip.kabelfon.vodafone.de
VoipBuster
www.voipbuster.com
Domain: sip.voipbuster.com
STUN Server: stun.voipbuster.com
VoipCheap
www.voipcheap.com
Domain: sip.voipcheap.com
STUN Server: stun.voipcheap.com
VoIPstudio
voipstudio.com
Domain: <SIP domain>
User Name: <SIP username>
VoipRaider
www.voipraider.com
Domain: sip.voipraider.com
STUN Server: stun.voipraider.com
VoIPtalk
www.voiptalk.org
Domain: voiptalk.org
User Name: 844xxxx
Connect using proxy: checked
Server: nat.voiptalk.org
Port: 5065
Vonage
www.vonage.com
Domain: sphone.vopr.vonage.net
Zadarma
zadarma.com
Domain: sip.zadarma.com