postfix interview questions

Explain the working of local mail submission for postfix?

When a local email message enters the postfix system. Local messages are deposited into the maildrop directory of the Postfix queue by the postdrop command, usually through the sendmail compatibility program. The pickup daemon reads the message from the queue and feeds it to the cleanup daemon. The cleanup daemon processes all inbound mail and notifies the queue manager after it has placed the cleaned-up message into the incoming queue. The queue manager then invokes the appropriate delivery agent to send the message to its next hop or ultimate destination.


What are the important files for postfix server ?

/etc/postfix/main.cf
/etc/postfix/access
/etc/postfix/aliases


Which command checks for configuration problems?

# postfix check


How you will see the queue of postfix server?

#postqueue -p 

or mailq


How can I clear postfix mail server queue?

# postsuper -d ALL


How you will reload the postfix queue?

# postsuper -r ALL


which command is used to find out that postfix is complied with mysql or not?

# postconf -m

nis
regexp
environ
mysql
btree
unix
hash


Explain smtpd_recipient_limit parameter? And what is the default value for this parameter?

The smtpd_recipient_limit parameter can limit the number of recipients allowed in a single incoming message.

The default value for this parameter is 1000.


Explain smtpd_timeout Parameter?

The smtpd_timeout parameter limits the amount of time Postfix waits for an SMTP client request after sending a response. This allows the Postfix administrator to quickly disconnect SMTP servers that "camp out" on the SMTP connection, utilizing system resources for the SMTP connection without actually sending a message.

smtpd_timeout = value

By default, Postfix will assume the value is in seconds.


Explain maximal_queue_lifetime Parameter?

The maximal_queue_lifetime parameter sets the amount of time (in days) that a message remains in the deferred message queue before being returned as undeliverable. The default value is 5 days. Once this value is reached, Postfix returns the message to the sender.


Explain queue_run_delay Parameter?

The queue_run_delay parameter sets the time interval (in seconds) that Postfix scans the deferred message queue for messages to be delivered. The default value for this is 1,000 seconds.


Explain default_destination_concurrency_limit Parameter?

The default_destination_concurrency_limit parameter defines the maximum number of concurrent SMTP sessions that can be established with any remote host. This parameter is related to the SMTP maxprocess parameter in the master.cf configuration file. The maximum number of concurrent SMTP sessions cannot exceed the maxprocess value set for the maximum number of SMTP client processes. Thus, if the default maxprocess value of 50 is used, setting the default_destination_concurrency_limit greater than 50 has no effect.




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