Several users wanted to block the top-level EU domain.
95% of my spam is coming from the EU TLD, but I can't find any way to block this stuff in Outlook's 'Junk E-mail Options'. For some reason "EU" isn't among the TLD's listed in International - Blocked Top-Level Domain List. I haven't found any way to add at TLD to the list.
I've also experimented with trying to catch these EU emails with a filter, but with no success. Is there any documentation about the use of wildcards ('*') in the search words of Rules (e.g. in Sender Address)?
Correct, EU isn’t on the Blocked Top-Level Domain List; .EU was launched in 2005, the International filter was added to Outlook 2003 in SP1, circa 2004. (UK is not on the list either, only GB.)
Search doesn’t support wildcards, so while you could look for .EU using a rule that looks for words in the header, there is a risk that it will trap legitimate email that just happens to have .EU in the header. You can also filter for sender domain, see Create rules that apply to an entire domain for the instructions. (EU is not used in many words so the damage such a rule may do shouldn’t be too great for most people.)
Filter EU using the International blocked list
Note: this adds EU to the Junk mail filtering capability, it does not add EU to the list of domains in the Blocked Top-Level Domain List. Only Microsoft can add EU to the dialog.
The International TLD’s you select in the Junk Email filter are stored in the registry under the profile key and you can add EU to the filter's blocked list by editing the registry. (The value name is not added to the registry until you block at least one International TLD.)
If you’re using Outlook 2013, the profile is stored at HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Profiles\<profile name>\. The International blocked domains list is stored in a separate key for each email account in the profile. Search for 001f0424, you’ll find this value name under a different key for each email account that blocking at least one TLD.
Outlook 2010 users will find their profile at HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\<profile name>\. As with Outlook 2013, the International blocked domains list is stored in a separate key for each email account in the profile and it's easier to find it by searching for 001f0424.
Outlook 2010, 2007, and 2003 profiles are stored at HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\<profile name>\. The International domains list is stored in the 0a0d020000000000c000000000000046 key, under value 001f0424.
This is a binary value and while it is editable, it’s not as simple as just typing in EU in the edit dialog. The easiest way to edit it is to add a TLD to the list that you don’t want blocked (such as ES) then select the individual letters to change them. Remove the letter by backspacing over it then type in E or U. For example: if you replace ES, select the S and type U. If you need to replace both letters, replace one letter at a time, you cannot select both letters in a TLD and type "EU".
If you want to block all domains, or you just want to be geeky, you can type the binary values in on the left. Click after a 00 and type 45 00 55 00 3B 00.
If you later edit the list using the Junk Email Option's Blocked Top-Level Domain List dialog, EU will be removed and you’ll need to re-edit the registry.
Add EU to the International Blocked TLD List Tutorial
If you want to block all UK messages (which I don’t recommend), you’ll need to add UK to the list as the GB selection does not block UK. (I also tested this with the INFO TLD and it didn’t work, you'll need to use a rule to block domains.)
Remember, if you have more than one account in Outlook 2010 or 2013, you’ll need to edit the registry key for each account, as each account has it's own junk mail options (and blocked/safe lists). The value won't be created for an account if you don't enable international filtering for that account.
How to check Junk Email settings for each account in Outlook 2010 and up: If you are using separate data files, select a message and look at the Junk, Junk Email Options, International tab. If you are delivering to one pst, open a message from each non-default account and choose Junk, Junk Email Options. Repeat for each account. The title bar on the dialog will show the name of the account whose junk settings you are looking at. For more information and screen shots, see Using Outlook's Junk Mail filter.