I installed sendgrid on my server today for the first time. Now I have several questions to you more experienced programmers.

1. Is there anything I should know about using sendgrid for server generated mails?

2. Can I still use my own configured Mail-Server (eg. for sending emails with Thunderbird?

3. How does sendgrid work?

4. Are there probably better alternatives? (I first wanted to use mailgun, but those fuckers want me to have a credit card for registration)