Lost email messages

I have a number of email accounts which I use for particular purposes to be organised.

I am extremely concerned at the loss of messages especially with no prior warning.

I am a college instructor and have lost very important information.

I did not realise that it is apparently possible to have them retrieved - I hope this is correct.

I would more than appreciate advice as to how to reinstate all messages removed in the change over to Outlook.

I must say that I am disappointed that such action was taken without prior warning or indeed why at all.

I look forward to a positive reply as soon as you are able to do so.

This account is one of my accounts in which all prior messages were removed.

My Thanks,

Ian.