If this is in your office then most likely you are behind a firewall of some sort. There aren't many companies out there who have no firewall at all between their network and the outside world. There are a couple of things to check. Thunderbird has a way to add email addresses, and domains etc. to safe senders list. I'm not positive what follows the @ symbol for MS emails, but maybe someone on the boards could look at a current email, and respond so you know which domain to allow access to. You can then follow these steps to add safe senders in Thunderbird on a PC.
Mozilla Thunderbird for PC
1. Click Address Book.
2. Make sure Personal Address Book is highlighted.
3. Click New Card. This will launch a New Card window that has 3 tabs: Contact, Address & Other.
4. Under Contact, enter the email address and additional information if you wish.
5. Click OK to finish .
Whitelist your Personal Address Book:
1. Click Tools.
2. Click Junk Mail Controls. This will launch the Junk Mail Controls window that has two tabs: Settings and Adaptive Filter .
3. Under Settings, update the White Lists module by selecting Personal Address Book from the pull down menu.
4. Check the box next to Do not mark messages as junk mail.
5. Click OK to finish.
The other thing to check is your antivirus program. Most of them have built in email filtering. One that comes to mind right away is Kaspersky. It needs to be "trained" to determine spam from not spam. However, I have seen a scenario when Kaspersky is first set up that allows the installer to tell Kaspersky what to do with mail that it determines is junk on its own prior to your "training". It can skip the message, and deliver it to your inbox, or there is an option to just delete it. If that option was chosen when it was installed, then it is entirely possible that Kaspersky (or other antivirus program which has similar settings), just deleted the email automatically. Your IT department should be able to look at some logs from the email server, and determine if someone sent an email to you which never made it to your inbox. If MS did in fact try to send it to you, there will be a record of the request hitting your company email server. That could help in determining where the mail ended up.
It might be easier for you to open a web based email account like gmail, hotmail etc., so that you don't have to deal with company filtering for personal emails.
Hope this helps.