Emails you send out of Method may have the following warning:
Be careful with this message
This may be a spoofed message. The message claims to have been sent from your account, but Gmail couldn’t verify the actual source. Avoid clicking links or replying with sensitive information, unless you are sure you actually sent this message. (No need to reset your password, the real sender does not actually have access to your account!)
This may be because of your "From" email address.
Your "From" email address is the same as the email address of the recipient.
The "Reply-to" email address differs from your "From" email address.
The "From" email address contains the same domain as the recipient email address domain (e.g., email@example.com and firstname.lastname@example.org).
In other words, if you are emailing yourself a test message, you will see this warning.
If you are not emailing yourself or your team members on the same domain, it's best to make sure the SPF records for the domain are configured correctly.