Many users have found that some Samsung smartphones automatically create a Junk folder and move valid emails to the folder without any set rules or interaction from the device user.
View a helpful article on the subject and a possible solution at the following link:
Spam filters are a client-level feature of Samsung's Email app on many Galaxy devices. To configure the settings, proceed through the following steps:
1. When email is filtered within the Email app, a Junk folder is created that syncs to the user's Exchange mailbox.
2. The feature allows users to block email addresses as spam and allows rules to be created that can block certain messages from reaching the Inbox. To access these features in the Email app, tap the Menu key and then Settings.
3. Tap General settings.
4. Tap Spam addresses.
5. Email addresses or domains can be blocked or removed in Spam addresses. In some cases, false positives are caused by an address that is mistakenly blocked.
6. Rules for filtering is also part of the spam filter feature, and can be accessed from General Settings. If messages are being moved to the Junk folder and the address is not listed in Spam addresses, check the Rules for filtering section for any rules that may be blocking the message(s).
7. The Rules for filtering section also allows messages containing set key words in subjects to be blocked from all or certain senders. As these rules are applied at the client level, messages must first reach the device before being filtered this way.