How it works

The tool begins by taking a beginning. The defaults are b, c, d, f, g, h, j, l, m, n, p, r, s, t, p, r, s, t, v, w.

Adding a middle. The defaults are the vowels a, e, i, o, u.

And then adding an ending. For example ble, ck, ct, de, ld, le, lk, ll, m, mber, mble, mpus, ndle, ng, nk, nt, pple, rce, re, rk, st, t, tile, tion.

The tool loops from the ending inwards:
the first run tries bable.com
the second run tries back.com
...
the 25th tries beble.com
...
the 121st tries cable.com
... and so on until all 2,400 combinations have been tried.

When I first ran the tool, only 92 of the 2,400 combinations were available!