Before reading further, please verify that Sendy's .htaccess file is uploaded in your Sendy folder on your server.

As part of the compatibility checklist, mod_rewrite needs to be enabled.

If you get a 404 error after installing Sendy, this means mod_rewrite may not be enabled.

Some hosts returns a 404 error even when it's enabled. To fix this, try adding the following line to Sendy's .htaccess file right after the line RewriteEngine On:

RewriteBase / if your installation URL looks like http://mydomain.com or http://sendy.mydomain.com

or

RewriteBase /sendy if your installation URL looks like http://mydomain.com/sendy

If both lines does not work, create a .htaccess file (if it does not exist) in your root directory with this line:

RewriteBase /

If everything fails, mod_rewrite is not enabled on your server, consult your host to enable mod_rewrite.