==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): ??
2021020901 (Backend: mariadb, Date: 2021-02-09 17:52:30) iRedMail Easy: https://www.iredmail.org/easy.html
- Linux/BSD distribution name and version: Centos 7.9.2009
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  mysql
- Web server (Apache or Nginx): apache
- Manage mail accounts with iRedAdmin-Pro? prü
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
Feb 18 14:23:48 mail postfix/smtpd[65485]: NOQUEUE: reject: RCPT from dd22134.kasserver.com[85.13.141.244]: 554 5.7.1 <dd22134.kasserver.com[85.13.141.244]>: Cl
ient host rejected: Generic - Please relay via ISP (kasserver.com); from=<xxx@xxx.com> to=<yyy@yyy.de> proto=ESMTP helo=<dd22134.kasserver.com>
====

The default rdns_access.pcre file contains the following regex:
/^dd[1-9][0-9]{3,5}\.kasserver\.com$/  REJECT Generic - Please relay via ISP (kasserver.com)

This makes it impossible to receive e-mails from any website hosted with all-inkl.com. The information given to use kasserver,com is misleading because emails are always delivered from subdomains with this ISP.

all-inkl.com is one of the largest ISPs in Germany and rejecting all e-mail messages by default is more than bad. whitelisting of customers is not possible because rdns_access.pcre is loaded in smtpd_client_restrictions  before the whitelisting smtpd_recipient_restrictions takes effect.

Please remove this regex.

Thanks you in advance

Michael