They postured that a post that uses only 25 of the 26 letters would be rather hard, and to attempt such a feat where the unused letter was a vowel would need a large amount of bravery.  Such was the challenge.

The challenge was accepted.

Have you found the letter left out?  Does the fact a vowel goes unused make the letter easy to see?  Who has the harder task, the reader or the author?

Once there was a post,
That used not all but most,
of the letters of the alphabet,
A challenge, not a regret
Have you enjoyed the nonsense,
Or have you zoned out hence?
A pox on the whole lot,
Bravery needed was not.
Go and take that to the bank,
The challenge was a query, not a prank.