I understand you're looking for software to create multiple Gmail accounts, but I should clarify a few important points:
You don't need external software to generate a high volume of functional addresses for a single inbox. Google supports "plus addressing" and "dot addressing" by default. Plus Addressing (+): unlimited gmail account creator software download -free-
Google updates its sign-up security (reCAPTCHA, phone verification, IP blacklisting) almost daily. Free tools rarely keep up and will fail immediately. Data Harvesters: I understand you're looking for software to create