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emailcalendaremail-validationemail-client

Can the underlying email provider be determined from an email address?

We are building a system that is, effectively, an email/calendar/contact client.

Users will provide us with their email address password (or other auth, eg oauth) and we will connect to their underlying email system.

"underlying systems" include:

  • Microsoft Exchange / Office365
  • GMail
  • Yahoo Mail
  • Apple email
  • Generic IMAP

Each of these systems have subtle (and not so subtle) differences in their APIs, especially to access calendar & contact data. Thus we need to know what provider the user is using.

But we would rather not ASK the user. We would like to figure it out (and at, least reduce the choices) automatically.

I've looked around for something that already implements this but have not found anything. I know it's mostly possible because Windows Phone does it pretty well (just enter username/pw and it does the right thing).

Before I dive in and start writing my own I want to ensure I'm not wasting my time if someone's already done it in an excellent way.

Know of anything like this? For this project prefer C#/.NET.

[EDIT: Adding potential algo]

Potential Algorithm:

  • Given email address & password
    • Extract domain name from email address
    • Try Exchange autodiscover. If successful done.
    • Use DNS MX records to find smtp host.
      • Do SMTP EHLO
      • Gmail responds with "250-mx.google.com at your service"
        • So if we see a "google.com" we are done.
      • Yahoo responds with 250-mta1257.mail.sk1.yahoo.com
        • So if we see a "yahoo.com" in the response we are done.
      • Apple responds with 250-xxxxxx-mac.com
        • So if we see a "mac.com" in the response we are done.
      • If none of the above
        • IMAP?
          • ...

[EDIT: 5/18] I built a prototype that uses methods that don't require auth (e.g. just MX/SMTP sluthing). Give it a try: http://bit.ly/KLZKxD

Solution

  • I created an implementation of this that has been used widely with some success: https://github.com/tig/Email2Calendar

    This is used by both milelogr.com and freebusy.io.