how can I get the log file,
if you mean maillog please find below. sample
Feb 20 03:31:54 custmail postfix/smtpd[1587]: connect from custmail.****[127.0.0.1]
Feb 20 03:31:54 custmail postfix/trivial-rewrite[2216]: warning: do not list domain cab.email in BOTH mydestination and virtual_mailbox_domains
Feb 20 03:31:54 custmail postfix/smtpd[1587]: 996E4407385B: client=custmail.****[127.0.0.1]
Feb 20 03:31:54 custmail postfix/cleanup[2058]: 996E4407385B: message-id=<20170220013154.996E4407385B@custmail.****>
Feb 20 03:31:54 custmail amavis[2456]: (02456-08) Passed CLEAN {RelayedInternal}, MYNETS LOCAL [10.10.200.65]:55555 <estatements@cab.email> -> <090700619@cab.email>, Queue-ID: 50B6D417A791, mail_id: bdC3R66cjgAT, Hits: 1.098, size: 199542, queued_as: 996E4407385B, 40432 ms, Tests: [ALL_TRUSTED=-1,HTML_MESSAGE=0.001,MISSING_MID=0.14,MPART_ALT_DIFF=0.724,TVD_RCVD_SINGLE=1.213,T_OBFU_PDF_ATTACH=0.01,T_REMOTE_IMAGE=0.01]
Feb 20 03:31:54 custmail postfix/smtp[2499]: 50B6D417A791: to=<090700619@***>, relay=127.0.0.1[127.0.0.1]:10024, delay=406235, delays=362299/43896/0/40, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp:[127.0.0.1]:10025): 250 2.0.0 Ok: queued as 996E4407385B)
Feb 20 03:31:54 custmail postfix/qmgr[30658]: 50B6D417A791: removed