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I am using Twilio's Verify API for authenticating my users through email and SMS by sending them an OTP.

So here are the observations and current situation.

  • SMS OTPs are almost instantly delivered
  • Email OTPs are sometimes instantly delivered and sometimes it takes 2 to 3 minutes.
  • There is no pattern in the slowness of Email OTPs
  • Talked to customer support but they failed to identify the root cause.

Has anyone else faced this type of peculiar issue while using Twilio's Verify API?

Thanks in Advance. Robin

Robin Panicker
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1 Answers1

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Just an update on how I solved this, since I feel it might be helpful for others (since no one answered it yet)

I talked to Twilio / Sendgrid support multiple times and we concluded that the slowness is due to one of the following reasons

  1. There is a n/w delay on the system from which the API is being called. This can be debugged by loggin on to the sendgrid admin console and checking the time (and status) of each request

  2. You might be using a free plan which limits your usage to 100 emails / day. Upgrade to essential plan that would assure a more reliable SLA. (My personal thought is that they are probably trying to move us into a paid subscription using diplomatic tactics. Anyways this again proves.. there is nothing like a free lunch)

  3. If it is a problem with specific email addresses or providers, then it could be possible that the sender domain / address has been blacklisted or marked as spam.

In our case, we migrated to the essential plan and that solved our issue.

Thanks, Robin

Robin Panicker
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