How to recover automatically deleted spam messages

I had sent an email some time ago in december , some weeks later the person told they had replied to me , but when i checked there was no mail. Later i relealized maybe it was in the spam folder, but it was not there either. May be it has been deleted as per the "delete spam after 30 days". I would very much like recover that mail , how can i do that ?
Thank you very much for the help.