really weird email glitch?

[RoyalGamer1]

so I use outlook for my email and recently I had to do a logitech RMA, I did the RMA on my computer but I started emailing them on my phone outtlook app. they said they sent the UPS return label but I never got it, I waited a long time then emailed them saying I didn't get it and them ended up just shipping me the mouse. but then today I go outlook on my computer and my email says I only have 9 emails (outlook on my phone has like over 800) and yes this is the exact same email I only have one. all the 9 emails are from UPS/logitech. it was the shipping label from USP 2 times and then  7 emails from logitech saying your UPS label is ready. and i guess in the "other" box I had a bunch of email from reddit i never knew I had. 

 

now my questions why are some emails on my phone app for outlook and not on my computer but the ones on my computer are not on my phone? is this a known thing? or just me?