postfix/postqueue[2332097]: fatal: malformed showq server response

[Torstens Bücherecke]

Hello,

since some months I'm getting the following error when running postqueue -p

Current postfix version on Ubuntu LTS is 3.6.4

postqueue -p failed : postqueue: warning: missing attribute protocol in input from public/showq socket postqueue: fatal: malformed showq server response

In the mail error log the error is: postfix/postqueue[2332097]: fatal: malformed showq server response

Is there any way to get more detailed information on that? Is there any configuration option which could be related to that error? I have reinstalled postfix alredy but that does not change anything.

Apart from that postfix seems to be running normal. Mails can be send and received without problems. Flushing of mail queue does work. If I take a look in the defer / deferred folders in /var/spool/postfix and mails can not be dropped for any reason (e.g. unknown recipient or something like this) they are visible in the folders.

Any Ideas? Currently I'm looking directly in the abovementioned folders if I would like to know if mails are in the queue because the command does not work.

[Torstens Bücherecke]

On the server where it's not working:
postqueue -p -v
postqueue: name_mask: all
postqueue: inet_addr_local: configured 5 IPv4 addresses
postqueue: inet_addr_local: configured 11 IPv6 addresses
postqueue: connect to subsystem public/showq
postqueue: public/showq socket: wanted attribute: protocol
postqueue: input attribute name: (end)
postqueue: warning: missing attribute protocol in input from public/showq socket
postqueue: public/showq socket: EOF
postqueue: fatal: malformed showq server response

On a server where it's working:
postqueue -p -v
postqueue: name_mask: all
postqueue: inet_addr_local: configured 7 IPv4 addresses
postqueue: inet_addr_local: configured 8 IPv6 addresses
postqueue: connect to subsystem public/showq
postqueue: public/showq socket: wanted attribute: protocol
postqueue: input attribute name: protocol
postqueue: input attribute value: mail_queue_list_protocol
postqueue: public/showq socket: wanted attribute: (list terminator)
postqueue: input attribute name: (end)
postqueue: public/showq socket: terminator (consumed)
Mail queue is empty

The difference seems to be
postqueue: input attribute name: protocol
postqueue: input attribute value: mail_queue_list_protocol
postqueue: public/showq socket: wanted attribute: (list terminator)