I needed to investigate, so I tried the method of relaying the sent mail, processing it, and then forwarding it to Office365.
WSL → telnet → Send mail → postfix → Process with Python → sendmail → It's like Office365.
I am using WSL (Ubuntu 18.04 LTS) of Windows 10 as an environment because it is only a confirmation of the implementation method. E-mail is sent from within WSL (localhost), and postfix settings are prioritized for operation check.
I started from an environment where WSL (Ubuntu 18.04 LTS) can be used on Windows 10 Pro.
Installation of WSL (Windows Subsystem for Linux) and initial settings of Ubuntu
http://www.postfix.org/FILTER_README.html https://qiita.com/kanedaq/items/aab362e20bdafea83fff
$ sudo apt install postfix
$ sudo cp /etc/postfix/main.cf.proto /etc/postfix/main.cf
$ sudo vi /etc/postfix/main.cf
#Mail system host name (FQDN)
myhostname = hostname.example.jp
#Mail system domain name
mydomain = example.jp
#Domain name (domain name) that is automatically completed when an email is delivered
myorigin = $mydomain
#Network interface to receive mail (all)
inet_interfaces = all
#Allowed network range
mynetworks = 127.0.0.0/8
#The full path of the Postfix sendmail command
sendmail_path = /usr/sbin/sendmail
#Full path of Postfix's newaliases command
newaliases_path = /usr/bin/newaliases
#Full path of Postfix mailq command
mailq_path = /usr/bin/mailq
#Group for sending email and managing queues
setgid_group = postdrop
#Postfix HTML document location
html_directory = no
#Postfix manual location
manpage_directory = /usr/share/man
#Location of Postfix sample configuration files
sample_directory = /etc/postfix
#Postfix README file location
readme_directory = /usr/share/doc/postfix
#Add from here to the bottom of the configuration file
#Top mail server of the forwarding destination (Office365 this time)
relayhost = [smtp.office365.com]:587
# SMTP-Enable AUTH
smtp_sasl_auth_enable = yes
#A file that describes the address of the transfer destination server and the user name and password to be authenticated.
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
#Do not allow anonymous login
smtp_sasl_security_options = noanonymous
#Filter for SASL mechanism on destination server
smtp_sasl_mechanism_filter = LOGIN
#TLS encryption if possible
smtp_tls_security_level = may
#CA certificate (ca-certificates）
smtp_tls_CApath = /etc/ssl/certs/ca-certificates.crt
$ sudo vi /etc/postfix/sasl_passwd
[smtp.office365.com]:587 Username (email address):password
$ sudo chmod 600 /etc/postfix/sasl_passwd
$ sudo postmap hash:/etc/postfix/sasl_passwd
$ sudo service postfix restart
$ tail -f /var/log/mail.log
$ cat /var/log/mail.err
#Check the process
$ ps aux|grep rsyslog|grep -v grep
#Check settings
$ sudo /usr/sbin/rsyslogd -n -d
$ cat /etc/rsyslog.d/50-default.conf
#Check the status
$ sudo /etc/init.d/rsyslog status
#Start the process
$ sudo /etc/init.d/rsyslog start
error: open database /etc/aliases.db: No such file or directory
#Stop Postfix and rebuild and start the mail alias database
$ sudo service postfix stop
$ sudo newaliases
$ sudo service postfix start
#Confirmation of existence of mail alias database
$ ls /etc/aliases.db
$ telnet hostname.example.jp 25
Trying 127.0.1.1...
Connected to hostname.example.jp.
Escape character is '^]'.
220 hostname.example.jp ESMTP Postfix (Ubuntu)
(input) HELO hostname.example.jp
250 hostname.example.jp
(input) MAIL From:Sender email address
250 2.1.0 Ok
(input) RCPT To:Destination email address
250 2.1.5 Ok
(input) DATA
354 End data with <CR><LF>.<CR><LF>
(input) This is test mail.
(input) .
250 2.0.0 Ok: queued as EAD291C000000084498
(input) quit
221 2.0.0 Bye
Connection closed by foreign host.
Make sure that you can receive the relayed mail with MUA (Outlook) that has an Office365 account set up.
If you cannot receive the email, check the log
$ tail -f /var/log/mail.log
$ cat /var/log/mail.err
$ sudo apt install python3
$ sudo apt install python3-pip
$ python3 -V
$ pip3 -V
$ cd ~
$ mkdir postfix
$ cd postfix
$ touch transfer_mail.py
$ chmod 755 transfer_mail.py
#!/usr/bin/python3
import sys
import os
import email
import email.parser
from os.path import join, dirname
from subprocess import Popen, PIPE
#Get from standard input
mime_str = sys.stdin.read()
# mime_str = open(sys.argv[4]).read()
#Analyze as email
message = email.parser.Parser().parsestr(mime_str)
#A file that spits out the contents of an email
filepath = join(dirname(__file__), 'result.txt')
#Exhale the contents of the email to a file
with open(filepath, mode='w') as f:
#Parameters
for arg in sys.argv:
f.write(f"{arg}\n")
#Email header
for key in message.keys():
value = message.get(key)
f.write(f"{key} : {value}\n")
#the content of the email
payload = message.get_payload()
f.write(payload)
#Set source, destination, subject
message["From"] = sys.argv[1]
message["To"] = sys.argv[2]
message["Subject"] = "Test mail !!!"
#Forward email
command = ["/usr/sbin/sendmail", "-t", "-oi"]
stdout = ''
stderr = ''
retval = 0
process = Popen(command, stdin=PIPE)
(stdout, stderr) = process.communicate(message.as_string().encode())
retval = process.wait()
if retval == 0:
sys.exit(0)
else:
sys.exit(1)
$ sudo vi /etc/postfix/master.cf
# content_Specify filter
smtp inet n - n - - smtpd -o content_filter=filter:dummy
# content_Define a filter (user to run, program to run, sender, recipient, size)
filter unix - n n - 10 pipe
flags=Rq user=User argv=/home/user/postfix/transfer_mail.py ${sender} ${recipient} ${size}
$ sudo service postfix restart
$ tail -f /var/log/mail.log
$ cat /var/log/mail.err
$ telnet hostname.example.jp 25
Trying 127.0.1.1...
Connected to hostname.example.jp.
Escape character is '^]'.
220 hostname.example.jp ESMTP Postfix (Ubuntu)
(input) HELO hostname.example.jp
250 hostname.example.jp
(input) MAIL From:Sender email address
250 2.1.0 Ok
(input) RCPT To:Destination email address
250 2.1.5 Ok
(input) DATA
354 End data with <CR><LF>.<CR><LF>
(input) This is test mail.
(input) .
250 2.0.0 Ok: queued as EAD291C000000084498
(input) quit
221 2.0.0 Bye
Connection closed by foreign host.
Confirm that the relayed mail was received by MUA (Outlook) for which the Office365 account is set.
Confirm that the text file is output
$ cat ~/postfix/result.txt
/home/user/postfix/transfer_mail.py ← Executed program
Sender email address ← Filter parameter 1
Destination email address ← Filter parameter 2
Size ← Filter parameter 3
Return-Path : <Relay email address>
Received : from hostname.example.jp (localhost [127.0.0.1])
by hostname.example.jp (Postfix) with SMTP id 923AE9E00000003FBF1
for <Destination email address>; Fri, 9 Oct 2020 23:55:00 +0900 (JST)
Message-Id : <[email protected]>
Date : Fri, 10 Oct 2020 23:55:00 +0900 (JST)
From :Sender email address
This is test mail.(Text)
$ tail -f /var/log/mail.log
Oct 10 23:55:00 hostname postfix/qmgr[10858]: 923AE9E00000003FBF1: from=<Sender email address>, size=362, nrcpt=1 (queue active)
Oct 10 23:55:00 hostname postfix/pipe[10951]: 923AE9E00000003FBF1: to=<Destination email address>, relay=filter, delay=591, delays=591/0.01/0/0.08, dsn=2.0.0, status=sent (delivered via filter service)
Oct 10 23:55:00 hostname postfix/qmgr[10858]: 923AE9E00000003FBF1: removed
Oct 10 23:55:00 hostname postfix/pickup[10857]: 2047A9F00000003FBF1: uid=1000 from=<user>
Oct 10 23:55:00 hostname postfix/cleanup[10955]: 2047A9F00000003FBF1: message-id=<[email protected]>
Oct 10 23:55:00 hostname postfix/qmgr[10858]: 2047A9F00000003FBF1: from=<[email protected]>, size=567, nrcpt=1 (queue active)
Oct 10 23:55:00 hostname postfix/smtp[10957]: warning: vstream_tweak_tcp: getsockopt TCP_MAXSEG: Protocol not available
Oct 10 23:55:00 hostname postfix/smtp[10957]: 2047A9F00000003FBF1: to=<Destination email address>, relay=smtp.office365.com[XXX.XXX.XXX.XXX]:587, delay=1.6, delays=0.03/0.02/1.1/0.4, dsn=2.0.0, status=sent (250 2.0.0 OK <[email protected]> [Hostname=XXXXXXXXXXXXX.xxxxxxxx.xxxx.outlook.com])
Oct 10 23:55:00 hostname postfix/qmgr[10858]: 2047A9F00000003FBF1: removed
I'm curious about the vstream_tweak_tcp warning in the log, but I was able to relay and process the email I sent and then forward it to Office365. It seems that it can be used for cooperation with other services and surveys during development.
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