Odd spam

A poster posted random gibberish on a post I made a few years ago. LJ had apparently filtered out 117 "suspicious" emails (with zero false positives), but the one reading "wqrzi18 glimw57 Ucjeo65 dkBes47 bDqse23 aptmy19 mleJq73 Oujcy46 yfzPx29" somehow got through (although I've turned on filtering so it wasn't actually posted).

Wondering what the purpose of this message is. May be a test string (so I rot13'ed it just to be safe) but I can't work out any more compelling idea.