How to verify Mandrill custom sending domain without a mail receiving client?

I was having the same problem earlier. I had a web application running on a server. So I configured incoming mails on mandrill by adding some MX records, then creating a route for the same domain for a random address which points to one of the POST endpoints on my web application.

So, whenever someone sends an email to that address, I get a POST request on the web endpoint which I put in the control panel. Mandrill gives a confirmation url in the email body. So, by inspecting the logs, we can directly copy the url and paste it in the browser and the domain is verified.

You can delete the incoming domain in mandrill afterwards if you don't need it.

I followed the advice but forth by Melyssa Griffin and used Google Suite to create an email address with domain of @mycompany.com. It was pretty easy to setup, though you do have access to your DNS system, and be willing to enter some credit card details. Be sure to cancel the suite services before 30 days or you'll be charged.

I was able to use the steps in this article to verify without setting up mail services. Similar to a previous answer but uses requestb.in.

1. set up MX records in Mandrill as per documentation
2. create new RequestBin https://requestb.in
3. add route to an email address e.g. admin@mandrill.example.com (this needn't be a working email address), which posts to the RequestBin e.g. https://requestb.in/wwxxyyzz
4. send domain verification email from Mandrill "sending domains" interface
5. the email should be viewable inthe RequestBin e.g. https://requestb.in/wwxxyyzz?inspect
6. find the verification link (may need to remove backslashes) in the raw email message and paste into browser to complete process

https://blog.ashfame.com/2016/11/verify-sending-domain-mandrill-email-hosting/