Human Readable Mailbox Delegations

Full Access

To get a specific mailbox:

Get-MailboxPermission -Identity "admin" | Select @{l='User';e={$User = Get-Mailbox -Identity $_.User | Select -expand DisplayName;if ($null -eq $User) {$_.User} else {$User}}},@{l='AccessRights';e={$_.AccessRights -Join ", "}}

To get all mailboxes:

$Mailboxes = Get-Mailbox
$FullAccessOutput = @()

foreach ($M in $Mailboxes) {
	Write-Host "Processing [$($M.Alias)]"
	$FullAccessOutput += Get-MailboxPermission -Identity $($M.UserPrincipalName) | Select Identity, @{l='User';e={$User = Get-Mailbox -Identity $_.User | Select -expand DisplayName;if ($null -eq $User) {$_.User} else {$User}}},@{l='AccessRights';e={$_.AccessRights -Join ", "}}
}

Send As

$Mailboxes = Get-Mailbox
$SendAsOutput = @()

foreach ($M in $Mailboxes) {
	Write-Host "Processing [$($M.UserPrincipalName)]"
	$SendAsOutput += Get-RecipientPermission -Trustee $($M.UserPrincipalName)
}