Email Sometimes Goes Into Wrong Folder

I have two email accounts on my Macbook running MacOS High Sierra. One email account is my iCloud email account which is my "Primary" email account. The second account is a TWC Roadrunner account which I only occasionally use. I have noticed over the past weeks that incoming email to my iCloud email address is being dumped into the Trash folder for the Roadrunner account. I am missing important work-related emails because of this. What are the steps to correct this situation? I never send out email using the RR account, only my iCloud account and mail replies to my iCloud account are ending up in the RR trash folder.