The problem: Outlook.com is automatically deleting Sent Mail messages from the Sent folder after three days. I want it to retain Sent messages until I choose to delete them.
Background: This issue started about a year ago. At that time, I had several Outlook.com email addresses (and the aliases associated with each of them) all forwarding into one Outlook.com client (hosted on subdomain bay178). I've been an Outlook.com user since its 2012 rollout, and did not experience this Sent message auto-deletion issue until 2015. I cannot find anything in Outlook.com's Settings options that pertains to Sent message retention.
Now, messages I send are visible in the Sent Mail folder for about 72 hours after sending, and then they simply disappear. They do not go into the Deleted or Archive folders. I keep my Inbox messages organized by conversation, and I am not sure if my replies - which would have originally appeared in the Sent folder, then disappeared after 3 days - are being preserved in these conversation threads or not. (I was able to find some conversations where my replies did appear, but those pre-date this auto-deletion problem.)
Around the same time, but for unrelated reasons, I decided to disable forwarding for one of these email/alias pairs in order to access it via its own separate instance of Outlook.com (hosted on subdomain blu172). This separation of accounts had NO effect on the way Sent messages were being auto-deleted after 3 days on the bay178 subdomain account, but (fortunately!) the blu172 Outlook.com profile does NOT exhibit the Sent messages auto-deletion behavior.
I have researched this issue extensively online but can only find comparable problems reported for Outlook, not Outlook.com. I tried chatting with MS tech support...two frustrating hours later, no joy. They assured me the problem was fixed, but it persists and is very annoying. Any ideas, suggestions, etc. are much appreciated!