On fresh TinyCP install I still have to do:

chmod +x /opt/tinycp/domains/

before LE verification process can be done successfully.

Warning: file_get_contents(/opt/tinycp/etc/opendkim/***.***/dkim.txt): failed to open stream: No such file or directory in /opt/tinycp/www/mods/mail/mail-server/inc/MailConfig.class.php on line 154

in domain / EMails tab.

"opendkim" folder doesn't exist and it's not created for new domain.

DKIM fixed :-D

But I still have problem with incoming mail. It's simply doesn't work. Check out this, maybe you can help:

Sep 22 18:06:38 kotek postfix/smtpd[19209]: connect from smtp8.dhosting.pl[195.88.50.182]
Sep 22 18:06:39 kotek postfix/spawn[19214]: warning: command /opt/tinycp/bin/postfix-policyd-spf-perl exit status 2
Sep 22 18:06:39 kotek postfix/smtpd[19209]: warning: premature end-of-input on private/policy-spf while reading input attribute name
Sep 22 18:06:40 kotek postfix/spawn[19214]: warning: command /opt/tinycp/bin/postfix-policyd-spf-perl exit status 2
Sep 22 18:06:40 kotek postfix/smtpd[19209]: warning: premature end-of-input on private/policy-spf while reading input attribute name
Sep 22 18:06:40 kotek postfix/smtpd[19209]: warning: problem talking to server private/policy-spf: Connection reset by peer
Sep 22 18:06:40 kotek postfix/smtpd[19209]: NOQUEUE: reject: RCPT from smtp8.dhosting.pl[195.88.50.182]: 451 4.3.5 <x@X.X>: Recipient address rejected: Server configuration problem; from=<x@X.X> to=<x@X.X> proto=ESMTP helo=<smtp8.dhosting.pl>
Sep 22 18:06:40 kotek postfix/smtpd[19209]: disconnect from smtp8.dhosting.pl[195.88.50.182] ehlo=2 starttls=1 mail=1 rcpt=0/1 data=0/1 rset=1 quit=1 commands=6/8

I've fixed problem with "warning: command /opt/tinycp/bin/postfix-policyd-spf-perl exit status 2"

There were Mail::SPF Perl module not installed which is necessary to run this script.

Quick solution (on Debian 9):

apt-get install build-essential
perl -MCPAN -e shell
install Mail::SPF

Never mind. Fixed with milter service fix:

1. Change in /etc/opendkim.conf

Socket inet:8891@127.0.0.1

2. Change in /etc/default/opendkim

SOCKET="inet:8891@127.0.0.1"

3. Change in /lib/systemd/system/opendkim.service

ExecStart=/usr/sbin/opendkim -P /var/run/opendkim/opendkim.pid -p inet:8891@127.0.0.1

But first you have to install libssl-dev :-D

apt install libssl-dev