Bug 9021 -- Add an exception to SMS via email documentation in the Koha manua -- was added to 16.05, but there is no documentation for adding SMS gateways nor adding the provider and sms number in the patron's messaging preferences.
I was incorrect -- SMS via email *is* documented, but SMS:Send is not.
What do you mean by SMS::Send?
(In reply to Katrin Fischer from comment #2)
> What do you mean by SMS::Send?
Koha can use the perl SMS::Send module to send SMS messages. See http://search.cpan.org/~adamk/SMS-Send-1.06/lib/SMS/Send.pm.
This requires the us of a SMS::Send driver, written for the SMS provider that the library chooses.
I think this is resolved for newer versions.