Among the common connection problems that may prevent MarsEdit from communicating with your blog is the deliberate blocking of WordPress’s API (the interface MarsEdit connects to your blog through) by your web hosting provider, or by a WordPress plugin. In these situations, it can be useful to “whitelist” MarsEdit so that it is allowed to access the API, even while requests from other sources remain blocked.
Whitelists can allow specific IP addresses to pass through, but since most MarsEdit users will not always be connecting from the same IP address, it is preferable to whitelist by “user agent”, which is a custom description of the app that is sent with every request to your blog.
MarsEdit’s user agent is consistent in its pattern, but contains a number of variable components such as the app version and the version of the operating system being used. For example:
MarsEdit/4.4.3 (Mac OS X/10_13_3; https://redsweater.com/marsedit/)
Because the user agent will always include the word “MarsEdit”, and because it is unlikely that any other app will include this word in their own user agent, we recommend setting up whitelists by user agent so that they grant access to any request that includes “MarsEdit” anywhere in the user agent.
If You Can’t Whitelist
Some hosts may not offer the ability to whitelist clients to WordPress’s API. If you are in this situation, and you have the ability to install custom WordPress plugins, you might be able to evade your web host’s security limitations by renaming the XMLRPC API endpoint. Here is a popular WordPress plugin that achieves this goal: