Do you write "letter of recommendation" on recommendation letter?
It’s frustrating to have to look for a bunch of emails titled “Letter of Reference” to find the one about a particular student or post doc candidate. Alternatively, if I’m on an online platform, I want to make sure I’m reading the right letter.

So, as a matter of convenience for anyone handling the letter, I include a header


  Letter of Recommendation for Anna Goodresearcher


or something similar as the subject of my letter. That way, it’s immediately obvious who the letter is for, making life easier for whoever is organizing or evaluating the applications. If it’s a postdoctoral reference or something else being sent directly to an individual by email, I try to include this in the email header as well.