Randomly Missing Outlook.com Emails

My problem lies with some emails that are sent to my school's email address (******* Email address is removed for privacy ***) that are being automatically forwarded to an Outlook Alias (****** Email address is removed for privacy ***) of my primary Outlook account (******** Email address is removed for privacy ***). 

Case 1: I was sent an email with a discussion thread by sender A. The thread contained a email previously addressed and sent to me by sender A, but I had never received it before, and it does not exist in my inbox. So I have proof that it was sent from sender A to me, but I had not received it. Sender A explained that he had never received an error email when sending it.

Case 2: I was expecting an email, but did not receive it. I emailed the individual, and they said that they sent it and did not receive an error email. This situation has occurred 5+ times.

Case 3: The IT people at my college looked at the log of my school emails. They found an email in Case 2 that was successfully received by my school email, and forwarded to my outlook email with no apparent error.

I have done the procedure detailed here: http://answers.microsoft.com/en-us/windowslive/forum/email/im-not-receiving-emails-sent-by-my-family-or/377a9bf3-7975-4d76-a6eb-04dcc6d68097, which includes the following:

1) Checked my Junk folder

2) Checked my Blocked sender list

3) Checked my Email Rules

4) Checked my Junk Mail Settings

5) Checked my Reply-to address

There is still a problem despite following the procedure above. This is a pretty frustrating situation, because I shouldn't have to worry about missing more time-sensitive internship-related emails.