You'll need to contact your mail administrator and ask them to trace those e-mails. Based on senders and destinations and approximate time gap when they were sent, they can check server logs and see if indeed they were delivered to your mailbox, if they were sent to a different address, etc.
That will depend on your institution policy whether they are permitted to perform such an audit and provide you with logs, etc., though.
Just by yourself it's complicated to prove you did not get those e-mails, server logs will probably provide a more robust answer to this.
3This is a bit of an X-Y problem. The real problem is that you were not made aware of the information sent by the institution. You simply let them know you did not receive the emails, as that is your experience. If they push back on this, they are being unprofessional. That is, unless you have reason to believe you are likely to forget such things, or unless you think the messages may have been automatically flagged as spam before you ever saw them. – called2voyage – 2017-11-07T16:03:50.413