Why is postfix not sending emails?

Question

postfix

Can you tell me why postfix is ​​not sending emails? logs:
To your mail:
Deferred: Connection timed out with mail.site.com
To yahoo mail:

postfix/postdrop[20748]: warning: unable to look up public/pickup: No such file or directory

Config.:

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_un$
myhostname = site.ru
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = $myhostname, localhost.$mydomain, $mydomain
relayhost =
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = loopback-only
inet_protocols = all

Answer 1

rights to look at, start with:

postfix check