Hello Riegreldeutt13,
I would first check that you have the password corresponding to the @Bluewin.ch account. This password is not the same as the one you use to enter the Swissom customer center or your webmail. This password can be reset in the customer center or the mySwisscom App https://www.swisscom.ch/myswisscom/
Second I would check, as already suggested here, that you use the setup guide https://emailsetup.swisscom.ch/guide or www.swisscom.ch/email-update
Alternatively you can use the following parameters directly (for experienced users)
Incoming mail server
IMAP4: imaps.bluewin.ch (Port 993)
POP3: pop3s.bluewin.ch (Port 995)
Use SSL
Authentication: Password
CRAM/Digest/MD5 deactivated
Outgoing mail server
SMTP: smtpauths.bluewin.ch (Port 465)
Use SSL
Authentication method: Password (sometimes also called Normal)
CRAM/Digest/MD5 deactivated
Hope this helps