Hi @Wu Rui Qiang ,
these original emails ended up missing from that Folder where they originally located.
Did this issue occur on any specific messages or all messages that you forwarded? If it occurred on any specific messages, are there any similarities on them?
And what's the type of your account(pop,imap or exchange)? In order to further confirm if these emails were missing in your mailbox, it's suggested to search it via type the subject in search field on your outlook client and web mail. At the same time, we could also try to forward the message in your web mail and check if you could work normally there, if you could search the message on your web mail or the issue only occurred on your Outlook, the issue may be more related to your client itself.
What's the version of your Outlook 2013(File>Office account>About Outlook), please first ensure that you have updated to the latest version of Outlook.
As I know, there seems to be no option in Outlook that could cause the message deleted after forwarded, considering the issue occurred on two users' client, did they have any similarities on their client(such as install any add-ins or other programs), in order to avoid the interference of Outlook add-ins and other programs, it's suggested to close other programs and restart your Outlook in safe mode for testing(windows + R>type "outlook.exe /safe">enter).
If the issue still exists, based on my research, it would also occur when your outlook data file is corrupted, it's suggested to repair your data file to check.
If your issue has any update, please feel free to post back.
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