I have a very unique situation. I manage rental property and when a tenant needs maintenance, they go to my website to fill out a form. Once the form is submitted, I receive a text to my cell phone and then an email. I need to be able to get this information on my Inreach Explorer when I'm out of cell service. At this point the info has to be texted to someone else then forwarded to me on my Inreach.
When I input the inreach number (mine has stayed the same since I've had the device for 4 years) to receive the automated texts, it sends a message to the number to verify that I am authorized to add that number. The problem is the inreach won't receive the verification text because it will only receive a text from a number it recognizes because it sent it a text first.
I do not know of any possibilities. I think that it has been designed to not accept any SPAM via Iridium. Consequently, it can only receive replies from devices to which it has sent an SMS.
To elaborate a little, your inReach does not HAVE a number. The number that you think of as "yours" is assigned dynamically when you send a message from the iR. The message you send arrives at the Garmin servers, along with the cell number(s) of the intended recipient(s). For purposes of the example, assume there is only one recipient because it makes things easier to understand. The Garmin servers ship the message and recipient number off to an SMS gateway, which chooses a number (from an available pool of numbers assigned to the gateway by its cell provider) from which to send the SMS message. The gateway reports that number back to the Garmin servers and sends the message from the assigned number. Garmin records the combination of the assigned number (which identifies the iR device in this conversation), the destination number, and the unique iR device ID (IMEI or whatever) in a table on the Garmin server.
SMS messages inbound to the gateway (replies) are handled as follows. The reply comes into the gateway for the dynamically assigned number from which the original message was sent. The reply is itself is from the number to which the original message was sent. The gateway forwards both numbers and the reply text to the Garmin servers. Garmin looks up the combination of numbers in the table in order to translate the reply target number into an iR device ID. That device is the target of the reply message sent by Garmin via the Iridium network.
The dynamically generated number from which the original message (iR to cell phone) was sent is entirely random. Depending on the size of the pool for the particular gateway, you may see the same number frequently. But there is no guarantee that it will not change from one message to the next, even in a very short time frame. In fact, depending on the recipient's cell phone number, subsequent messages may be sent by an entirely different gateway.
Also, the lifetime of the table entry which maps the pair of phone numbers to the iR device ID is limited. Garmin does not retain them forever. If somebody tries to reply to a message that was sent months ago, the reply may not be delivered because the table entry is gone. This is why best practice in normal (off the grid hiking or whatever) circumstances is to "prime the pump" by sending a message to your frequently used contacts when you start each trip. That way, the table has a fresh entry and replies will be delivered reliably.
As I'm sure you know, MapShare provides a mechanism for sending messages to iR devices in the field. However, I doubt that you want your tenants using that mechanism directly.
You can check with your cell phone service provider to see if there is any provision for forwarding SMS messages. If so, you could use that, plus a pump-priming message to your own number, to handle the situation. But most providers do not forward SMS.
Edited to add: There are commercial services which provide SMS forwarding. I have no idea what they cost, or how easy/difficult it is to change the number to which SMS messages are forwarded. If this is important enough to you, this kind of service might provide a solution.
To add to twolpert's post WRT to expiration: 1. When I plan to go out of cell coverage, I send an SMS to those that may want to get in touch with me. 2. I suggest that they save it so that they can reply to it if they want to get back to me. 3. Then, prior to next trip, I repeat the outgoing SMS in case the previous has expired.
Wanted to give an update for anyone looking to do what I wanted to do with my Inreach. I used an app called If This Then That (IFTTT) to accomplish what I needed. I would send a test text from the inreach to a cell phone that has service so that phone could text my inreach later. When that phone would receive the text that I needed to forward, I would have the app (IFTTT) automatically forward that text to my inreach. This would work because the app sends a text from the cellphone number that had already received a text the inreach. When IFTTT sends an automatic text it sends it from the cell number that is running the app instead of sending it from temporary number like other services do.
