Understanding the Safe and Blocked Senders lists

Last reviewed on September 20, 2014   —  51 comments

How the blocked sender’s filter works seems to a point of confusion for a number of Outlook users. It does not block the messages sent by those addresses from being downloaded; Outlook needs to download the messages in full (not headers only) to run the filters.

Blocked senders are treated as Junk Email and the messages will be handled the same way as mail filtered by the Junk Mail filter. It’s either placed in the Junk Mail folder or deleted, per your Junk mail options.

More Information

Safe Senders listFor this reason, and the reasons listed below, it is highly recommended that you add names to the Safe lists (to avoid false positives) and let the Junk Mail filter take care of the junk. The blocked list should be short.

My own blocked list has 2 addresses on it. One is a person who forwards a lot of stuff and the other is a newsletter I can’t get unsubscribed from. I don’t add people I send mail to, to my Safe Senders list because I reply to a lot of people just once or twice and my list would fill up fast, but it is recommended for most users.

If you choose to trust mail from addresses in your Contacts and you created a contact for yourself, all mail sent to you will be trusted.

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.

For example, if you have 1800 addresses on the safe list, you can only block approximately 200 addresses. If the addresses are long, your list will hold fewer addresses; if they’re short, you’ll be able to have more.

Microsoft imposed the limit to improve performance, as the lists are stored as a hidden property in the Inbox and duplicated to the local registry. Each time the users synchronize with the Exchange mailbox store, the lists are downloaded. The limit can be adjusted on Exchange server, by adding a new registry key value to the following registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ ParametersSystem\
DWORD: Type Max Extended Rule Size
Value Data: maximum size (in bytes) that you want to allow

Importing a list of blocked addresses from an older version of Outlook is not recommended, in part because these lists often are larger than 512K and Outlook crashes when trying to import them, but also because spammers change addresses so often that lists are outdated within a few months.

If Outlook’s Junk email filter doesn’t offer enough options, misses too much spam, or you need better Safe and Blocked lists, try one of the many excellent third party anti-spam filters available.

For a list of third party tools, visit Rules and tools to filter junk mail in Microsoft Outlook

Outlook needs to use cached mode with Exchange server mailboxes to filter junk email on the client side. In classic online mode, any junk mail that is filtered is done so by the Exchange server’s filter.

For Exchange server junk mail filtering tools, visit Content Control Tools for Exchange Server

Customize the filter?

Is there a way to add a group of selected junk e-mail from the inbox to the blocked senders list all at one time instead of one junk e-mail at a time?

The short answer is simply No. The long answer is that while it seems like a really stupid move by Microsoft not to include this functionality, or the often requested ability to train the filter, they have an excellent reason for not including these options.

Microsoft believes that users should not have to touch the filters period. Any antispam solution should be automatic and good enough to catch most spam, because as we’ve learned over the years with antivirus software and Windows updates, users aren’t very good at keeping their programs updated. It also takes time to tinker with antispam settings and filters, time better spent doing anything but configuring the filters.

If the filter is designed right, only a few addresses will need to be added to any of the lists – such as addresses belonging to people you don’t want to correspond with or whose messages are mistakenly classified as spam. In fact, adding every address that is used the send spam to the list will result in a long list of names, many of which will never send you another message. In addition, you are limited to approximately 2000 names on all of the lists combined and would need to spend a lot of time culling the list. (See Outlook 2003’s Safe and Blocked Senders Lists for more information on the size of the lists.)

Your goal should be to have a Safe senders list longer than your Blocked senders list. If you need to spend minutes each day (or following each mail pass) adding addresses to your Blocked list, then your Junk Email settings are too low, you don’t have the latest filter update, or you need a better spam filter than the one provided with Outlook. Businesses should filter out the spam on the email server, removing spam long before the messages are downloaded to their users desktop.

How long are my lists? My Safe Senders and Safe Recipients lists contain 24 addresses and domains, while the blocked senders list contains just two addresses.

Delete addresses from the Blocked list

If you receive an error that your list is full or you just want to clean up the list, open the Junk Email Options dialog and delete names from the lists. In Outlook 2010 and 2013, open it from the Home tab, Junk button, Junk Email Options.

Remove names from the blocked list

When you use an Outlook.com account, you need to log into the account online and remove the names from the blocked list (or verify they were removed when you removed them in Outlook.)

Written by

Diane Poremsky
A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

Please post long or more complicated questions at Outlookforums.

51 responses to “Understanding the Safe and Blocked Senders lists”

  1. anita

    I keep getting junk spam and I want to select them from the junk folder, lets say 20, and then add them to the blocked senders list at one time. is this possible? help.

  2. Eva

    I have been receiving the mail from the Sender which I would like to Block. I clicked few times the Outlook icon but it did not stop sending me new. What I should do to fix my problem. I use Outlook 2007.

  3. John

    I subscribe to a number of newsletters which use other organisations to deliver their messages. Can I set up a safe senders list entry with wildcard entries i.e. *.*.mcsv.net as I want to be able to download photos immediately from these emails.

  4. sarah carlson

    My daughter's emails sent from Germany are returned to her as undeliverable. How can I change outlook to allow her messges to be delivered to me? I have never blocked or removed block's so hopefully the process is simple!

  5. Debbie Weltin

    why do blocked senders keep showing up in inbox?

  6. bgagnon

    When outlook is parsing through the 200 addresses it can see, is it doing this alphabetically or in the order in which they were added? Seems to be aphabetical but want to confirm. Thanks!

  7. donna

    how do i find out if my block list is full?

  8. aud2093 ("Audy")

    Where can I see the Safe Senders list? Email addresses, e.g. Amazon Book Deals, that I add to the Safe Senders list are still not automatically downloading the images even though the Automatic download settings are set to allow image downloads from safe sender list emails and trusted domains.

  9. Audy

    Thank you so much!!

  10. Doug

    Did something change in how Outlook 2013 handles safe senders? In Outlook 2010, a message from a sender that uses our company domain name is considered safe and it will automatically display the images within that message. In Outlook 2013, it will NOT display the images. Thoughts?

  11. Doug

    Thanks for your response. We don't include our corporate domain on the safe list(it's automatically removed anyway). Yes, we trust any addresses from the GAL. I don't believe there's been any upgrades to Exchange recently. I'm actually accessing the same mailbox on two different machines, one running Win 7/Outlook 2010 and the other running Win 8/Outlook 2013. Inline images for the same message item are automatically rendered on the 2010 machine and not rendered on the 2013 machine. I've confirmed that we've removed the domain that hosts the message content from the IE trusted sites list on both machines. Seems kind of odd.

  12. John

    Hello Diane,
    Every time I get spam mail I click to put into the block list but the window pops saying cannot block because it's in your contacts and then it show's my email. So I tried trying to find my email on my contacts list so I can erase it and it's not there. I emailed myself a few times in the past and I was wondering if that is why but still why would my email not show up on my contact list? I don't get this cannot block message!

  13. John

    it''s Outlook but formerly Hotmail if that helps. I went to gear box but nothing there that says delete myself from my contact "senders box" list.

  14. John

    It's number 2. By the way when I get spam some I can block others the message I always get when I click on the block button is "we have deleted the message but since they are a part of your contact list, we couldn't block" How is that possible I don't have any spam address in my contacts? Only my friends,family and my email which only appears in number 2.

  15. Tom Hall

    Hi - I've got an intermittent (Outlook 2013 x64, on Windows 8.1), problem adding to the Safe Sender's List

    I have several "regular" (non-spam) emails, but Outlook prevents downloading pictures "to protect my privacy".

    I really do want to see the pictures, so, I click on the message, and select either "add the sender", or "add the domain" to the Safe Sender's list

    Problem is that although I can now see the pictures in the email, if I then view the Junk mail options / Safe Sender's list, sometimes the sender / domain has been added, and sometimes it hasn't been added.

    Any suggestions ?

  16. Tom Hall

    Hi - I have two POP accounts delivering to the same PST. As to the Automatic Downloads settings, all the boxes are selected.

  17. Tom Hall

    I also have my PST stored on a WSE2012 R2 network share, so that I can access it from both my pc & laptop (though not at the same time)
    I know having a PST located on a network is not supported etc, but I've done it this way since WindowsHomeServer v1), and never had any corruption problems.
    Also, I usually cut to using a new PST each year for filing purposes, and also when I change to a new version of the Outlook

  18. Tom Hall

    I've just been reading http://support2.microsoft.com/kb/2252421 - although this article starts off saying it's for group policy, it does later on refer to non-policy reg settings (which I don't have), and seems to imply that these reg keys are needed for Safe Sender's list to work ?

  19. Emma

    I hope you can help - I have been receiving emails from a person I do not want to correspond with, who has effectively been cyber-stalking me for the last few months. He has recently found out my work email address and I have added him to my blocked senders list. All his emails are routed to junkmail automatically, and are then deleted. What I'm nervous about is understanding whether, when I turn on Out of Office Automatic Replies, will he receive these messages? Or are these not sent to Blocked Senders? Appreciate your guidance!!!

  20. lil hunsaker

    how do I get rid of senders on my block list. I keep getting the msg that my block list is full and I need to delete some items.

  21. Keith

    Is there anyway to defeat the spammers who use variable domain names? I get a lot of junk from @mail* (where * is a number from 1 to ?) followed by .us*.mcsv.net or .atl*.rsgsv.net or .wd*.mcdlv.net. If limited to 999 I can see that there are 3 million possible addresses just from these examples. Spammers are one maybe 10 steps ahead of Microsoft Outlook on this one.

  22. Dennis

    Hi Diane,

    I have added people to Safe Recipients list and checked the box to download images from people on the list in Trust Center. But yet, they are still blocked. Any ideas? Thanks in advance for the help!


  23. Dennis

    It is for a POP account. Yes, they are direct emails from someone (might be a generic email - like info@whatever.com) but still that is the "to" email address. There may be a name attached to - for example: Jane Doe I did just test with another email address and the safe recipient still did not work (no name, email address listed in "to" only). thanks for the help. Dennis

  24. Dennis

    Ok, thanks. LMK!

  25. Donna

    Does an addressee added to my blocked sender list receive any notification from my email address when messages are blocked?

  26. John Davison

    I am a plastic Surgeon and use email to communicate with patients. Because of SPAM settings, and the words I use in my correspondence, many of my emails get lost in junk folders, and its a real problem.

    If a patient sends an email to me first, will my subsequent reply emails get through as "safe"?

    Any advice you have would be much appraciated.

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