Sent emails not showing up in Iphone sent folder unless sent from Iphone

Sent emails not showing up in Iphone sent folder unless sent from Iphone

Not sure if I have a setting wrong or this is just how it is -- emails sent from the phone do show in the sent mail everywhere (phone, web, thunderbird.) However, iphone sent emails are ONLY showing up in that iphone sent mail folder. Is thjere a way to fix this?

Using IMAP, iphone, thunderbird etc.