Some email boxes do not get any email - sieve discard

On my new set up mailinthebox,
some email boxes do not receive email, other with the same domain name does.
in the mail log I do this line. I did not configure any blocking rules or sieve rules.

It may be a bug on dovecot but why on some mailboxes it do work and on some not?
I do not see what is different, but guessing the must be a set up reason.
Therefore I did removed the mailbox and did recreate it but got the same result.

Aug 02 10:16:22 lmtp(<5250><0IoPJ9QQymSCFAAAbUD+ww>: Info: sieve: discard action: Marked message to be discarded if not explicitly delivered (discard action)

I found the following comments in the web:
its a bug, but the workaround is to
so postfix tempfail before lmtp delivery the first time
hopefully it credited you report this problem

But I do not understand how to fix it.

Does some experienced similar issues and was able to solve it?