Since updating my MacBook Pro to macOS High Sierra, I'm having troubles with my Mail app. My work mail, which uses the Exhange feature, does not receive any e-mail while the app is already open. All my other mail accounts like Gmail and iCloud work like they always do. I have to manually stop the app and re-open it to receive mails on the Exchange account, after which I won't receive any other mails that are sent while it's open. Sending them isn't a problem, but earlier today I had an issue where my Mail app would crash if I sent an email with the Exchange account. The mail would still be sent, but the Mail app kept crashing until I turned off the Exchange account in system preferences. This issue has been magically solved and I don't know how I or my system did this. If anyone knows what's up, please feel free to leave a comment here. Thanks in advance!