Email causes postmaster to send undeliverable message, yet using the same email address, my yahoo.com account sends the mail without problem.

This is the mail system at host ewsoutbound.kpnmail.nl.I'm sorry to have to inform you that your message could notbe delivered to one or more recipients. It's attached below.<kokobal@charter.net> failed: host mx0.charter.net (47.43.18.9) said: 550 5.1.0 <andynic@xs4all.nl> sender rejected. Please see https://www.spectrum.net/support/internet/understanding-email-error-codes for more information AUP#In-1010 (in reply to MAIL command)

Reporting-MTA: dns; ewsoutbound.kpnmail.nlReceived-from-MTA: dns; smtp.kpnmail.nl (10.31.155.7)Arrival-Date: Sat, 30 Sep 2023 22:50:35 +0200X-Original-ID: 010b6d84-5fd3-11ee-b453-005056994fdeFinal-Recipient: rfc822; kokobal@charter.netAction: failedStatus: 5.1.0Remote-MTA: dns; mx0.charter.net (47.43.18.9)Diagnostic-Code: smtp; 550 5.1.0 <andynic@xs4all.nl> sender rejected. Please see https://www.spectrum.net/support/internet/understanding-email-error-codes for more information AUP#In-1010 (in reply to MAIL command)