come (in) over the transom
To be offered without prior agreement, consent, or arrangement; to be unsolicited or uninvited. Said especially of written works submitted for publication or consideration. My biggest task as an intern was sorting through and usually disposing of amateur works that came over the transom. Any journalist will tell you that a great story doesn't come in over the transom—you have to go and do the leg work to find one.
over the transom
(hyphenated if used before a noun) Without prior agreement, consent, or arrangement; unsolicited or uninvited. Said especially of written works submitted for publication or consideration. My biggest task as an intern was sorting through and usually disposing of amateur works that came over the transom. I could tell the poor kid needed a job, but all I could do was stick his application in with all the other over-the-transom applications.