Some times there may be a necessary that you may have to set mailbox quota prohibitsendandreceive to unlimited. Some users may be very important person and you need to set UNLIMITED to atleast receive emails.

$username = <username>

Set-Mailbox $username -UseDatabaseQuotaDefaults:$False -issuewarningQuota 90MB -ProhibitSendQuota 100MB -ProhibitSendReceive “UNLIMITED”

This is to set explicity for a user, if you want to send similar setting to multiple people then you have have to loop it and apply the same or

get-content “C:\names.txt” | Set-Mailbox  -UseDatabaseQuotaDefaults:$False -issuewarningQuota 90MB -ProhibitSendQuota 100MB -ProhibitSendReceive “UNLIMITED”

get-content “C:\names.txt” | Set-Mailbox  -UseDatabaseQuotaDefaults:$False -issuewarningQuota “UNLIMITED” -ProhibitSendQuota “UNLIMITED” -ProhibitSendReceive “UNLIMITED”