Email Seeding: How to create multiple email accounts w/out phone verification?

Hi!

I work for a marketing firm and I am in the process of creating a seed list to track for partner email violations. I am having issues creating multiple Gmail/Yahoo email accounts due to the required phone verification.

I have attempted to use my personal Skype number, Google Voice number, and misc. other free third party number providers. However, when I attempt to verify the account using these numbers, I am greeted with "This phone number cannot be used for verification" prompt.

I have also attempted to create emails using the instructions found on this link (https://www.quora.com/What-is-a-way-to-create-many-Gmail-accounts-without-mobile-number-verification). However, upon signing in, Gmail reports unusual activity and requires me to verify via phone or sms-- resulting in the same aforementioned issues.

I am hoping someone here may have a solution to my issue or may be able to point me to a forum where I could continue to troubleshoot this problem.

Thanks for any help. I appreciate it.