The site's connection to an SMS service: sign-in codes, notifications and the site's other text messages are sent through it.
The provider list depends on the default language
When the site's default language is Farsi, the providers are Melipayamak Console, Melipayamak Dedicated Line (free text) and the LogaTech OTP subscription. Otherwise they are Twilio, Vonage and Plivo. The default language is set on the Language & Format tab. The list stays hidden until the language has loaded.
Manage permission only
This tab needs "Manage domains and credentials".
A dedicated line alongside a one-time-code provider
The Melipayamak dedicated line is for free-text informative and marketing messages, not one-time codes. You can set it up alongside one of the pattern-based providers; sign-in codes keep going through the pattern-based one.
The LogaTech OTP subscription needs a connection to LogaTech
It has no fields. Saving it fails unless this install is connected to LogaTech. When a connection exists, a Buy more link may appear for topping up.
Secrets are not shown again
After saving you see only a "Configured" status and a masked preview. To change even one field, enter every field for that provider again. Clear deletes the credentials without asking.
The test is real
The test button sends a real SMS to the number you enter, with the saved credentials, and it costs what a real message costs. Providers that work only with patterns cannot send free text, so their test sends a random six-digit one-time code instead; if you receive a numeric code rather than the test text, the test succeeded.
For Melipayamak Console the remaining message count is shown, with a refresh. It is a message count, not money, and it quietly shows nothing if the provider cannot be reached.