Apparently, his letter was unreadable and when asked to resend it, he never did.
From the orlandosentinel.com
Charlie Watts seems as impassive as the Sphinx, his eyes unreadable as he drums.
From the thenewstribune.com
This hashes a users IP address, making it unreadable to users other than IRCops.
From the en.wikipedia.org
It's pretty unreadable at the moment, and my limited French can't do it justice.
From the en.wikipedia.org
Since then, radio contact has been broken off and the beacon has been unreadable.
From the washingtonpost.com
He shows me the latter's 2004 album sleeve, featuring an unreadable hieroglyph.
From the guardian.co.uk
The idea of encryption is to make a message unreadable, except to the receiver.
From the economist.com
The one we viewed seems to have a mark, but it is unreadable in the image sent.
From the orlandosentinel.com
And if the document for example has two columns per page, basically unreadable.
From the guardian.co.uk
More examples
Indecipherable: not easily deciphered; "indecipherable handwriting"
(unreadably) illegibly: in an illegible manner; "this student writes illegibly"
Readability is defined as reading ease, especially as it results from a writing style. Extensive research has shown that easy-reading text improves comprehension, retention, reading speed, and reading persistence. ...
That cannot be read or is not easy to read; Not sufficiently interesting to be worth reading