How to find a mailbox that can't be found in Exchange?

Question

Mail server

Faced one problem. For one site, an existing mailbox with a username and password was needed. Nobody knows the password. I decided to reset my password, but here's the catch: I can't find the mailbox either in AD or in Exchange.
It does not find Get-Mailbox in Exchange Shell, and when created with the same name, it adds a deuce at the end. I can't delete, I can't create. I'm afraid I got this after the migration. The same problem with other boxes - I can not find data on them ..
Where to look? :)

Answer 1

in aliases looked?
generally look at get-recipient your_email_alias - to whom this address is attached

Answer 2

PowerShell Script

add-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010 -ErrorAction SilentlyContinue
$email=Read-Host 'What is eMail?'
get-recipient -results unlimited | where {$_.emailaddresses -match $email} | select name,emailaddresses,recipienttype|Out-GridView

Shows what is attached to the mailing address - a mailbox, a public folder, a distribution group, an alias
And by partial correspondence...