outlook 365 auto deletes emails after replying

[RSchellens]

Dear all,

Please help I'm at the end of my rope. 
Outlook often deletes emails after I have replied to them.

I say often as it seems hit and miss, I do not find a clear structure behind this.

I seem unable to find the option that does this in order to turn it off.

in the option section on conversation cleanup I have ticked all the "don't move" boxes

this is not a retention problem, as retention is set at 6 months and this also happens when the email is ten minutes old.

[#2]

Does it happen in Outlook Web or just Outlook Client?

[#3]

@AdminSeanMc 

Dear Sean,

I almost solely from the outlook app in windows 10.

I do have it installed on an android phone as well, but rarely use it there.
When I notice it, this is on the client in Win10.

[#4]

If you could, try work from the web client for a day, I'd bet it's a rule or setting/bug in your version of Outlook.