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introluxFlag for United Kingdom of Great Britain and Northern Ireland

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Office 365 - Block Sender Max Amount

Hi Experts,

I know the answer to this question:

How many addresses can the safe and blocked lists hold?
Approximately 2000 total. This is because the total size of all lists combined cannot exceed 512K. Once the 512K limit is reached, Outlook alerts you and additional addresses aren’t saved until you remove some from the list.

My issue is we have mas amount of email addresses that we would like to block and I have managed to do a registry hack within Exchange to increase the file size limit. However moving onto Office 365, we are not able to hack their system.

The question I have, is there a way of adding a domain to be blocked? for instance @domain200.com. So anything that comes from xxxxx@domain200.com is blocked. Like a wild card, this would reduce the amount of email addresses that we currently have.

Regards,

introlux
Avatar of Vasil Michev (MVP)
Vasil Michev (MVP)
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You can block based on domain via Transport rules, check for example here: https://technet.microsoft.com/en-us/library/dn198251(v=exchg.150).aspx

Or if you plan to do this on per-user basis, use the Get-MailboxJunkEmailConfiguration cmdlet. It accepts domains names.
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ASKER

Using Get-MailboxJunkEmailConfiguration cmdlet I can block sender via domain?
Well, it's actually Set-MailboxJunkEmailConfiguration, but yes, you can block by domain as well.
But can this be set per user? Also what is the limit?
Another question, how can a user manage this using a GUI? As every example I see is done via powershell.
ASKER CERTIFIED SOLUTION
Avatar of Vasil Michev (MVP)
Vasil Michev (MVP)
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I have just added Hotmail.com in the block sender list and it has still allowed an email address from xxxxx@hotmail.com to hit the inbox.......... ??????

Any ideas why?