550 5.7.1 Submission has been disabled for this account

If you are migrating from Exchange 2007 to Exchange 2010 and 2007 users are getting the following error when e-mailing 2010 users:
   The following recipient(s) could not be reached:
   Nuno
   (…)
   nuno@letsexchange.com
   HTCAS1.letsexchange.com #550 5.7.1 Submission has been disabled for this account # #
   (…)


and you see the same error on the 2007 Transport Logs for that e-mail:
    Source:          SMTP
    EventID:         FAIL
    Recipients:      {nuno@letsexchange.com}
    RecipientStatus: {550 5.7.1 Submission has been disabled for this account}
    (...)


be aware that this is (most likely) due to a bug (not confirmed with Microsoft) with Exchange 2010...


If your 2007 users have the following set for their mailboxes:
    UseDatabaseQuotaDefaults: True
    ProhibitSendReceiveQuota: 0KB
    ProhibitSendQuota:        0KB


This is what’s causing the issue! Although they are still able to e-mail 2003 and 2007 users, they can’t send e-mails to 2010 users due to the way Exchange 2010 checks the user’s quotas, even though they are set to use the database defaults!...


To check if this has already happened to any of your users, run the following command to check your transport logs for the error message mentioned before:

Get-TransportServer | Get-MessageTrackingLog -ResultSize Unlimited -Start "01/09/2011" -EventID FAIL | ? {$_.RecipientStatus -match "550 5.7.1 Submission"} | Select *, {$_.Recipients}, {$_.RecipientStatus} | Export-Csv D:\Nuno\550.csv -NoTypeInformation

To see if you have any users with 0KB quotas:

Get-Mailbox -ResultSize Unlimited -Filter {UseDatabaseQuotaDefaults -eq $True} | ? {$_.ProhibitSendReceiveQuota -eq 0KB -or $_.ProhibitSendQuota -eq 0KB} | Select Alias, ProhibitSendReceiveQuota, ProhibitSendQuota, UseDatabaseQuotaDefaults

and to correct them, run the following:

Get-Mailbox -ResultSize Unlimited -Filter {UseDatabaseQuotaDefaults -eq $True} | ? {$_.ProhibitSendReceiveQuota -eq 0KB -or $_.ProhibitSendQuota -eq 0KB} | Set-Mailbox -ProhibitSendQuota unlimited -ProhibitSendReceiveQuota unlimited

Note: 2010 users with 0KB quotas and using the database quota defaults are still able to e-mail 2010 and 2007 users!

Hope this helps!