The mail server could not deliver mail to The account or domain may not exist, they may be blacklisted, or missing the proper dns entries.

Message not sent. Requested action not taken: mailbox unavailable Server replied: 550 Verification failed for <> The mail server could [...]

Find Command

Here is a basic find command in a linux terminal through ssh: find / -name 'filename.txt' So that would search for an exact filename of filename.txt in any [...]