Echo Limiter Prevents FreeSwitch Voicemail Functionality
If you experiencing issues while trying to leave a Voicemail due to 'Your recording was below acceptable levels' or similar errors try turning off the recommended 'Echo Limiter' in Linphone's settings.
I experienced this problem on the latest version of Linphone for Android when calling my FreeSwitch setup. Testing from a land line and with other soft phones worked as expected, changing 'record-silence-threshold' and 'record-silence-hits' FreeSwitch's mod_voicemail settings had not effect, and hence through the process of elimination the culprit was determined to be the 'Echo Limiter' setting.
Saving you hours and hair; so do +1 this.