( http://bit.ly/2to5Y50 ) – the error “553 sorry, that domain isn’t in my list of allowed rcpthosts”

To fix it, do the following:

1. log into your mail server as root;
2. stop qmaild:

/etc/rc.d/init.d/qmaild stop

1. backup all needed files in the ~vpopmail/etc directory;
2. delete the directory ~vpopmail/etc:

rm -rf ~vpopmail/etc

1. create it anew:

mkdir ~vpopmail/etc

1. copy backed files to this new directory;
2. empty the file ~vpopmail/etc/open-smtp:

cat /dev/null > ~vpopmail/etc/open-smtp

1. start qmaild:

/etc/rc.d/init.d/qmaild start