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The challenge for Twilio is that phone #s are a fixed quantity. The same #s have been circulating across lots of different companies including being used by spa

The challenge for Twilio is that phone #s are a fixed quantity. The same #s have been circulating across lots of different companies including being used by spammers and in marketing campaigns and published across the Internet. Make sure to search the Internet for any phone # you acquire from Twilio before buying it. It may already have substantial call spam/undesirable organic traffic associated with it. On the flip side, there are already companies out there specializing in monetizing misdials. They specifically look for phone #s that have been retired recently with a lot of volume and then take those calls and resell as leads for cars, insurance, etc.

ben_jones 9y ago
Odds are you won't be able to figure that out. Furthermore downstream providers will often treat traffic differently, including but not limited to ratelimiting and dropping of SMS, if the number was abused by a previous owner. The things that people gloss over in an IPO...
- WisNorCan 9y ago
  Agree you won't be able to figure it out 100%. A couple of lines codes counting # of websites that reference the phone # will prevent some potential catastrophic results, but not all.
- softawre 9y ago
  Couldn't you test that though? I mean, test if your SMSs are dropped, or if you get ratelimited somewhere?
  - toomuchtodo 9y ago
    You have to acquire (at a cost) a number first to do that.
gregorymichael 9y ago
Greg from Twilio here. Agreed on the challenge of working with a fixed number of phone numbers (and I say this as someone who recently moved to NYC and would love to own a 212 number). In the industry, phone numbers that have a high-volume of unwanted traffic are called "dirty numbers." Think of a number used by someone who signed up for every sweepstakes they came across for 40 years, or maybe a number that's particularly cute (you probably don't want to have a cellphone tied to XXX-867-5309). If we sold them, dirty numbers would be worse-than-useless for (almost all) of our customers. So, whenever a phone number is released by a Twilio customer, we reserve it for a minimum of two months before it can be purchased by another account. We also monitor each reserved number until it reaches an acceptably low number of phone calls. If you do find yourself getting unwanted calls, you can use the <Reject>TwiML verb[^1] to create a blacklist - your account won’t receive or be charged for those calls. [1]: https://www.twilio.com/docs/api/twiml/reject https://www.twilio.com/docs/api/twiml/reject
- etjossem 9y ago
  SendGrid engineer here. We have a similar challenge in working with the fixed number of IPv4 addresses we're able to get our hands on. We offer our customers dedicated IP addresses for outbound email, but there are sometimes situations where a customer doesn't want to hold onto one forever. We want to make sure mailbox providers (like Gmail and Hotmail) have time to realize the IP is not in use, rather than mistakenly associating it with the old customer. It makes sense to hold onto it for a while after the customer releases it before allowing another customer to purchase it. We call this the "cooldown period."
  - linkregister 9y ago
    Gmail primarily uses domains for reputation, according to their docs (and in practice). I never had to deal with much IP management when sending to Gmail or G Suite recipients. Microsoft does use the range of black holes, e.g. Spamhaus, including using their own, so etjossem is right about having to cool down a bad IP before requesting whitelisting. Almost all ESPs and black holes will reject whitelisting requests without a sufficient cool down period anyway. Gmail is certainly ahead of its time. I haven't tried sending with IPv6 addresses but the Gmail documentation claims it will work.
Splines 9y ago
Slightly OT question - if I want a particular phone number, whats the preferred method of doing this? I.e., is there a way to be notified when someone gives up a certain number?
- c22 9y ago
  When I got my prime phone number I wrote a script that hooked into Google voice and Broadvoice's number requisition forms and looked through all the available numbers for suitable candidates every hour. I had the advantage of having many numbers that could meet my criteria, though. If there's just one specific number you want you might try calling it and seeing if you can negotiate a transfer?

ben_jones 9y ago

Odds are you won't be able to figure that out. Furthermore downstream providers will often treat traffic differently, including but not limited to ratelimiting and dropping of SMS, if the number was abused by a previous owner. The things that people gloss over in an IPO...

WisNorCan 9y ago
Agree you won't be able to figure it out 100%. A couple of lines codes counting # of websites that reference the phone # will prevent some potential catastrophic results, but not all.
softawre 9y ago
Couldn't you test that though? I mean, test if your SMSs are dropped, or if you get ratelimited somewhere?
- toomuchtodo 9y ago
  You have to acquire (at a cost) a number first to do that.

gregorymichael 9y ago

Greg from Twilio here. Agreed on the challenge of working with a fixed number of phone numbers (and I say this as someone who recently moved to NYC and would love to own a 212 number). In the industry, phone numbers that have a high-volume of unwanted traffic are called "dirty numbers." Think of a number used by someone who signed up for every sweepstakes they came across for 40 years, or maybe a number that's particularly cute (you probably don't want to have a cellphone tied to XXX-867-5309). If we sold them, dirty numbers would be worse-than-useless for (almost all) of our customers. So, whenever a phone number is released by a Twilio customer, we reserve it for a minimum of two months before it can be purchased by another account. We also monitor each reserved number until it reaches an acceptably low number of phone calls. If you do find yourself getting unwanted calls, you can use the <Reject>TwiML verb[^1] to create a blacklist - your account won’t receive or be charged for those calls. [1]: https://www.twilio.com/docs/api/twiml/reject https://www.twilio.com/docs/api/twiml/reject

etjossem 9y ago
SendGrid engineer here. We have a similar challenge in working with the fixed number of IPv4 addresses we're able to get our hands on. We offer our customers dedicated IP addresses for outbound email, but there are sometimes situations where a customer doesn't want to hold onto one forever. We want to make sure mailbox providers (like Gmail and Hotmail) have time to realize the IP is not in use, rather than mistakenly associating it with the old customer. It makes sense to hold onto it for a while after the customer releases it before allowing another customer to purchase it. We call this the "cooldown period."
- linkregister 9y ago
  Gmail primarily uses domains for reputation, according to their docs (and in practice). I never had to deal with much IP management when sending to Gmail or G Suite recipients. Microsoft does use the range of black holes, e.g. Spamhaus, including using their own, so etjossem is right about having to cool down a bad IP before requesting whitelisting. Almost all ESPs and black holes will reject whitelisting requests without a sufficient cool down period anyway. Gmail is certainly ahead of its time. I haven't tried sending with IPv6 addresses but the Gmail documentation claims it will work.

Splines 9y ago

Slightly OT question - if I want a particular phone number, whats the preferred method of doing this? I.e., is there a way to be notified when someone gives up a certain number?

c22 9y ago
When I got my prime phone number I wrote a script that hooked into Google voice and Broadvoice's number requisition forms and looked through all the available numbers for suitable candidates every hour. I had the advantage of having many numbers that could meet my criteria, though. If there's just one specific number you want you might try calling it and seeing if you can negotiate a transfer?