Same question as this: Paypal sandbox account email confirmation but it was not so easily resolved for me.
I can\'t confirm my sandbox email address, it says an emai
On Developer site is section Dashboard then Sandbox notifications - there are emails and sms from sandbox account, and also it catches confirmation emails which should go to your email...
I found it after one day of looking what's happend with email confirmations -.- .
If you're using Adapative Accounts API to create account (in the first place), put confirmEmail as TRUE in createAccountWebOptions (for registrationType = Web).. this way you wouldn't have headache of email confirmation, for new accounts.
Turns out the answer was not to try manually create a sandbox account on the sandbox website, but to automatically create one at developer.paypal.com > Applications > Sandbox Accounts. This was much quicker and easier to do too!