How can I send mail using php mail function and have anchor tag work for my email template

Question

I have tried sending a test mail using below mail template with php mail function but when this email came to a gmail inbox output was not the expected. Below are the snippets.

mail template:

Hi <name>,

Here is the subject of your order: <subject text with link to order>

Thanks,

What I received:

Hi Yen,

Here is the subject of your order: <a href="https://www.someurl.com/link/orderid">subject text with link to order</a>

Thanks,

Here is what I expected:

Hi Yen,

Here is the subject of your order: subject text with link to order

Thanks,