To Whom It May Concern is a letter salutation that is used in business correspondence when you don't have a specific person to whom you are writing.
It is appropriate to use To Whom it May Concern when making an inquiry, but you don't have a contact person to address your letter to.
When addressing a letter To Whom It May Concern, the entire phrase is typically capitalized, then followed by a colon:
To Whom It May Concern:
Read More: More Cover Letter Salutations | Letter Writing Guide | Letter Samples
Susannah addressed her cover letter To Whom It May Concern because there was no contact person listed in the job posting.