Email is still the backbone of most outreach. The provider you choose affects how easily you can send, connect tools and avoid limits.
Gmail
Widely trusted and easy to connect to almost any tool. Gmail accounts with an app password already set up save a step when you connect SMTP senders or mail clients.
Outlook and Hotmail
A good second provider so all your sending does not rely on one company. Microsoft accounts also open Teams and OneDrive.
Regional mail
If you target Poland, an Onet.pl mailbox looks more natural to local recipients than a foreign address.
Whichever you choose, warm each inbox up gradually and keep daily sending within sensible limits.