Sorry, I tested on Email 2 (Beta) but there it just works. On default mail I have the same line and the same problem you have.
The mails are there:
[root@testserver ~]# ls /var/lib/nethserver/vmail/vmail+testmailbox/Maildir/new
1522011564.M634870P16930.testserver.domain.local,S=962,W=986 1522011674.M486198P17201.testserver.domain.local,S=988,W=1012
My /var/log/maillog
:
[root@testserver ~]# tail /var/log/maillog
Mar 25 23:01:14 testserver postfix/qmgr[15919]: 647C530A6A94: from=<admin@domain.local>, size=748, nrcpt=1 (queue active)
Mar 25 23:01:14 testserver postfix/smtpd[17194]: proxy-accept: END-OF-MESSAGE: 250 2.0.0 Ok: queued as 647C530A6A94; from=<admin@domain.local> to=<dsfkjshgfjsdhf@domain.local> proto=ESMTP helo=<192.168.1.187>
Mar 25 23:01:14 testserver postfix/smtpd[17197]: disconnect from localhost[127.0.0.1]
Mar 25 23:01:14 testserver dovecot: lmtp(17201): Connect from local
Mar 25 23:01:14 testserver postfix/lmtp[17200]: 647C530A6A94: to=<dsfkjshgfjsdhf@domain.local>, relay=testserver.domain.local[/var/run/dovecot/lmtp], delay=0.11, delays=0.02/0.04/0.01/0.04, dsn=2.0.0, status=sent (250 2.0.0 <dsfkjshgfjsdhf@domain.local> V//EGxoOuFoxQwAArFJgQg Saved)
Mar 25 23:01:14 testserver postfix/qmgr[15919]: 647C530A6A94: removed
Mar 25 23:01:14 testserver dovecot: lmtp(17201, dsfkjshgfjsdhf@domain.local): V//EGxoOuFoxQwAArFJgQg: sieve: msgid=<acfb3ba11533024a057db2b4ca34eb1d@domain.local>: stored mail into mailbox 'INBOX'
Mar 25 23:01:14 testserver dovecot: lmtp(17201): Disconnect from local: Successful quit
Mar 25 23:01:14 testserver postfix/smtpd[17194]: disconnect from localhost[127.0.0.1]
Mar 25 23:02:24 testserver clamd[12884]: SelfCheck: Database status OK.
But they are not in roundcube:
