That sounds like your email carrier requires authentication-before-sending, and your email app isn't set to authenticate on sending. So it authenticates on receiving, then the authentication is good if you reply fairly soon.
Delete your email account from your email app, then add it again (as an existing account). Let the app set everything up, don't try to set anything, especially the SMTP settings, up manually. The app should authenticate, then download all the emails you had in it before. And you should be able to send emails without receiving one first.