We are planning an academic study in which we would recruit participants from outside Mechanical Turk and then ask them to first sign up for MTurk to be able to participate in the study. This protects their anonymity (as we would only know their MTurk ID and nothing else) and enables easy and secure payments of participation fees.
Ideally, once participants sign up for MTurk and (after accepting the consent form etc) input their MTurk ID in our anonymous web form, we would invite them to the actual study through MTurk. However, it seems that it is not possible to contact workers who did not yet perform a HIT for us.
We could ask them for their email addresses but we wish to avoid that to ensure complete anonymity.
We also know that we can simply post a study HIT on MTurk and enable access to it only for the workers with particular IDs, but without an email notification many participants might not notice this.
In sum, is there any way to send an email notification about a HIT to MTurks who did not yet work for us?
