Salutation for a letter of recommendation to be uploaded to mathjobs What is a standard opening salutation for a letter of recommendation to be posted on mathjobs?  

One possibility might be, "Dear hiring committee", or "Dear search committee".
Most of my math recommendation letters do not have an opening salutation.  They have the date at the top right, and the first sentence orients the reader with something like "I write to recommend Dr. X to you for..." If I recall correctly, this is fairly typical for such letters.  I am more confident in saying it doesn't matter: in general, the format for these letters is all over the place, and no one cares.