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Comment by JadoJodo | Hacker News Reader

I'd love to see a write up on this

I'm sure everyone's setup is different but I did this for about 8 years and had to stop recently due to a variety of problems. The first being the lack of support for group messaging. I couldn't send group messages at all but what was even worse was that when I was part of group messages I would receive the messages individually as if the person was texting me directly. My system could mark them as being group messages but I couldn't see the other recipients so there was no way of knowing who else was in a thread until other people started texting and then could piece together the group from context.

Also some services straight up refuse to send SMS to cloud phone providers meaning you can't sign up for certain services that needed a verified phone number (unless they had an option to receive a call with the verification code which worked like 25% of the time).

Dialing was another huge issue, you can somewhat intercept outbound calls on Android but the system is buggy so I had to find other methods. Since I had integrated my SMS/MMS messaging with Slack (one slack channel per phone number) I created a /dial command that would call my phone and then when I answered it would transfer me to the person I wanted to call.

Happy to answer more questions about it but I highly recommend people think about all the consequences before moving their main number over.

> Also some services straight up refuse to send SMS to cloud phone providers meaning you can't sign up for certain services that needed a verified phone number (unless they had an option to receive a call with the verification code which worked like 25% of the time).

I've ran into the same issue with this on Google Voice. Though sometimes I wonder if I could have gotten the best of both worlds by just porting a number from a traditional carrier to Google Voice/Twilio.

Are these kinds of checks only against the number itself? Or is there some kind of dynamic registry?

I have a number in Google voice that I ported from a regular old T-Mobile SIM years ago. I haven't seen many that won't send me an SMS message, but when I do, they are usually banks. I don't think it much matters where the phone number originates.

I’m almost certain the check is against what the number is behind. Also the opposite situation - Google Voice to carrier would result in issues if carrier to GV was fine. Not the case however.

The number needs to be non-VoIP. Off the top of my head, Uber, Lyft, Craigslist all require non-voip which means no Google Voice.

They have databases that they look up, but they're notoriously inaccurate. If you can use a number from another country (not always possible since some services require an in-country number, but a surprising number don't) you'll often find it works better, especially if you choose a country where the database provider might have less access to information about which ranges are assigned to which providers.

Google Voice has been my primary number for about 10 years and it usually works.

My main concern is what to do when Google kills it.

"Are these kinds of checks only against the number itself? Or is there some kind of dynamic registry?"

In general it is much simpler than that. These companies are sending you these SMS messages not from a "normal" phone number (xxx-yyy-zzzz) but from a shortcode (xxxxx). The "from" is a shortcode and only mobile numbers can receive SMS from shortcodes.

So if your number is not a "mobile" number, you might still receive SMS from other real phone numbers, but you cannot receive SMS from shortcodes.

Twilio, for instance, does not provide mobile numbers. Period. So even if you port a mobile number to twilio, as soon as it is theirs, you cannot receive SMS from shortcodes.

Your assertion that only mobile phones can receive SMS from shortcodes is not true in general, and additionally many verification SMS are not sent from shortcodes.

Only true mobile phone numbers can receive SMS from shortcodes.

Here is a list of carriers that are properly registered to receive SMS from shortcodes:

https://usshortcodedirectory.com/faq/what-wireless-carriers-...

"... short code carriers have arrangements to exchange messages with mobile phone numbers only ..."[1]

[1] https://support.twilio.com/hc/en-us/articles/223133447-Not-R...

I guess this is a US thing, then. It's definitely not true in general, as I said.

I’ve been considering a similar move and would also love to hear more about anyone who has made such a transition.

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