Sendmail概述:
Sendmail是最重要的郵件傳輸代理程序。理解電子郵件的工作模式是非常重要的。一般情況下，我們把電子郵件程序分解成用戶代理，傳輸代理和投遞代理。 用戶代理用來接受用戶的指令，將用戶的信件傳送至信件傳輸代理，如：outlook express、foxmail等。而投遞代理則從信件傳輸代理取得信件傳送至最終用戶的郵箱，如：procmail。 當用戶試圖發送一封電子郵件的時候，他並不能直接將信件發送到對方的機器上，用戶代理必須試圖去尋找一個信件傳輸代理，把郵件提交給它。信件傳輸代理得到了郵件後，首先將它保存在自身的緩衝隊列中，然後，根據郵件的目標地址，信件傳輸代理程序將找到應該對這個目標地址負責的郵件傳輸代理服務器， 並且通過網絡將郵件傳送給它。對方的服務器接收到郵件之後，將其緩衝存儲在本地，直到電子郵件的接收者查看自己的電子信箱。 顯然，郵件傳輸是從服務器到服務器的，而且每個用戶必須擁有服務器上存儲信息的空間（稱爲信箱）才能接受郵件（發送郵件不受這個限制）。可以看到，一個郵件傳輸代理的主要工作是監視用戶代理的請求，根據電子郵件的目標地址找出對應的郵件服務器，將信件在服務器之間傳輸並且將接收到的郵件緩衝或者 提交給最終投遞程序。有許多的程序可以作爲信件傳輸代理，但是sendmail是其中最重要的一個，事實證明它可以支持數千甚至更多的用戶，而且佔用的系統資源相當少。不過，sendmail的配置十分複雜，因此,也有人使用另外的一些工具，如qmail、postfix等等。當sendmail程序得到一封待發送的郵件的時候，它需要根據目標地址確定將信件投遞給對應的服務器，這是通過DNS服務實現的。
郵件服務器加密和驗證的準備工作：
郵件服務器正常使用一般需安裝如下軟件：
sendmail-8.13.8-2.el5.i386.rpm
sendmail-cf-8.13.8-2.el5.i386.rpm
m4-1.4.5-3.el5.1.i386.rpm（默認已安裝）
1.安裝sendmail-cf
[root@localhost Server]# rpm -ivh sendmail-cf-8.13.8-2.el5.i386.rpm
2.查看sendmail運行的端口
[root@localhost mail]# netstat -tupln |grep sendmail
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 2674/sendmail: acce
3.編輯sendmail.mc文件
[root@localhost Server]# cd /etc/mail
[root@localhost mail]# vim sendmail.mc
116 DAEMON_OPTIONS(`Port=smtp,Addr=0.0.0.0, Name=MTA')dnl
4.重啓sendmail服務
[root@localhost mail]# service sendmail restart
Shutting down sm-client: [ OK ]
Shutting down sendmail: [ OK ]
Starting sendmail: [ OK ]
Starting sm-client: [ OK ]
5. 再次查看sendmail運行的端口
[root@localhost mail]# netstat -tupln |grep sendmail
tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 3299/sendmail: acce
6. 在該域組內添加兩個用戶
[root@localhost mail]# useradd user1
[root@localhost mail]# useradd user2
[root@localhost mail]# echo "123" |passwd --stdin user1
[root@localhost mail]# echo "123" |passwd --stdin user2
7. 設置中繼
[root@localhost mail]# vim access
在access文件中添加如下
10 Connect:192.168.2.100 RELAY
8. 重啓sendmail服務
[root@localhost mail]# service sendmail restart
9. 測試能否給192.168.2.100 發/收郵件
[root@localhost mail]# telnet 192.168.2.100 25
Trying 192.168.2.100...
Connected to 192.168.2.100 (192.168.2.100).
Escape character is '^]'.
mail from:[email protected]
220 localhost.localdomain ESMTP Sendmail 8.13.8/8.13.8; Wed, 21 Mar 2012 11:53:43 +0800
250 2.1.0 [email protected]... Sender ok
rcpt to:[email protected]
250 2.1.5 [email protected]... Recipient ok (will queue)
quit
可以發/收郵件
10.在local-host-names文件中添加本地域名
[root@localhost mail]# vim local-host-names
bj.com
11修改access文件
[root@localhost mail]# vim access
Connect:192.168.2 RELAY
sh.com RELAY
bj.com OK
12.DNS服務器的配置
bj架設自己的DNS服務
1.安裝有關dns服務器的主要軟件包
[root@localhost Server]# rpm -ivh bind-9.3.6-4.P1.el5.i386.rpm
[root@localhost Server]# rpm -ivh bind-chroot-9.3.6-4.P1.el5.i386.rpm
[root@localhost Server]# rpm -ivh caching-nameserver-9.3.6-4.P1.el5.i386.rpm
2.複製named.caching-nameserver.conf文件並命名爲named.conf
[root@localhost Server]# cd /var/named/chroot/etc/
[root@localhost etc]# cp -p named.caching-nameserver.conf named.conf
3.編輯name.conf文件
[root@localhost etc]# vim named.conf
15 listen-on port 53 { any; };
27 allow-query { any; };
28 allow-query-cache { any; };
36 view localhost_resolver {
37 match-clients { any; };
38 match-destinations { any; };
39 recursion yes;
40 include "/etc/named.rfc1912.zones";
4.編輯區域聲明文件（正/反方向解析）
[root@localhost etc]# vim named.rfc1912.zones
複製15-19 並修改
20 zone "bj.com" IN {
21 type master;
22 file "bj.com.db";
23 allow-update { none; };
24 };
5.生成數據庫文件
[root@localhost etc]# cd ../var/named/
[root@localhost named]# cp -p localhost.zone bj.com.db
6.編輯數據庫文件
[root@localhost named]# vim bj.com.db
7.設置開機自動啓動dns，並啓動dns服務
[root@localhost named]# chkconfig named on
[root@localhost etc]# service named start
Starting named: [ OK ]
8.設置dns指向
[root@localhost etc]# vim /etc/resolv.conf
nameserver 192.168.2.100
9.編輯network文件
[root@localhost named]# vim /etc/sysconfig/network
HOSTNAME=mail.bj.com
10編輯hosts文件.
[root@localhost named]# vim /etc/hosts
127.0.0.1 mail.bj.com localhost.localdomain localhost
11.重啓系統
[root@localhost named]# init 6
12．查看dns和sendmail服務器的狀態
[root@mail ~]# service named status
server is up and running
named (pid 2378) is running...
[root@mail ~]# service sendmail status
sendmail (pid 2704) is running...
13.檢測dns能否解析
[root@mail ~]# nslookup
> set q=any
> mail.bj.com
Server: 192.168.2.100
Address: 192.168.2.100#53
Name: mail.bj.com
Address: 192.168.2.100
14.使用Windows測試內部郵件的發送
使用Outlook Express 步驟如下:
完成user1賬戶的創建
創建郵件併發送：
發送後在sendmail服務器日誌上查看
[root@mail ~]# tail -f /var/log/maillog
Mar 21 17:03:22 mail sendmail[3336]: q2L93MSd003336: from=<[email protected]>, size=409, class=0, nrcpts=1, msgid=<AA961B346B454E0884074973A8AA3E43@usergsc>, proto=SMTP, daemon=MTA, relay=[192.168.2.10]
Mar 21 17:03:22 mail sendmail[3339]: q2L93MSd003336: to=<[email protected]>, ctladdr=<[email protected]> (500/500), delay=00:00:00, xdelay=00:00:00, mailer=local, pri=30566, dsn=2.0.0, stat=Sent
可以看出已經成功發送！！！
14.爲郵件服安裝接受郵件服務器（dovecot）
[root@mail ~]# yum install -y dovecot
15.編輯dovecot文件
[root@mail ~]# vim /etc/dovecot.conf
修改如下：
20 #protocols = imap imaps pop3 pop3s
21 protocols = imap pop3
16.設置dovecot服務爲開機自動啓動，並重啓該服務
[root@mail ~]# chkconfig dovecot on
[root@mail ~]# service dovecot restart
Stopping Dovecot Imap: [ OK ]
Starting Dovecot Imap: [ OK ]
17.查看運行該服務的端口
[root@mail ~]# netstat -tupln |grep dov
tcp 0 0 :::110 :::* LISTEN 3507/dovecot
tcp 0 0 :::143 :::* LISTEN 3507/dovecot
18.檢測郵件能否正常接收
[root@mail ~]# tail -f /var/log/maillog
Mar 21 17:40:02 mail dovecot: Dovecot v1.0.7 starting up
Mar 21 17:40:02 mail dovecot: Generating Diffie-Hellman parameters for the first time. This may take a while..
Mar 21 17:40:09 mail dovecot: Killed with signal 15
Mar 21 17:40:09 mail dovecot: Dovecot v1.0.7 starting up
Mar 21 17:40:09 mail dovecot: Generating Diffie-Hellman parameters for the first time. This may take a while..
Mar 21 17:45:41 mail dovecot: pop3-login: Login: user=<user1>, method=PLAIN, rip=::ffff:192.168.2.10, lip=::ffff:192.168.2.100
可以看出users1能正常接受郵件！！！
郵件服務器的加密與認證
查看編譯信息
[root@mail ~]# sendmail -d0.1 -bv
Version 8.13.8
Compiled with: DNSMAP HESIOD HES_GETMAILHOST LDAPMAP LOG MAP_REGEX
MATCHGECOS MILTER MIME7TO8 MIME8TO7 NAMED_BIND NETINET NETINET6
NETUNIX NEWDB NIS PIPELINING SASLv2 SCANF SOCKETMAP STARTTLS
TCPWRAPPERS USERDB USE_LDAP_INIT
============ SYSTEM IDENTITY (after readcf) ============
(short domain name) $w = mail
(canonical domain name) $j = mail.bj.com
(subdomain name) $m = bj.com
(node name) $k = mail.bj.com
========================================================
Recipient names must be specified
[root@mail ~]# telnet 127.0.0.1 25
Trying 127.0.0.1...
Connected to mail.bj.com (127.0.0.1).
Escape character is '^]'.
220 mail.bj.com ESMTP Sendmail 8.13.8/8.13.8; Fri, 23 Mar 2012 15:54:24 +0800
EHLO 127.0.0.1
250-mail.bj.com Hello mail.bj.com [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-DELIVERBY
250 HELP
QUIT
發送郵件服務器
starttls（smtp+ssl）
建立服務器證書
[root@mail ~]# cd /etc/pki/CA/
[root@mail CA]# cd ..
[root@mail pki]# vim tls/openssl.cnf
45 dir = /etc/pki/CA # Where everything is kept
88 countryName = optional
89 stateOrProvinceName = optional
90 organizationName = optional
[root@mail CA]# mkdir crl certs netcerts
[root@mail CA]# touch index.txt serial
[root@mail CA]# echo "01" >serial
創建CA私鑰
[root@mail CA]# openssl genrsa 1024 >private/cakey.pem
Generating RSA private key, 1024 bit long modulus
..............................................++++++
........................................++++++
e is 65537 (0x10001)
[root@mail CA]# chmod 600 private/*
創建ca證書
[root@mail CA]# openssl req -new -key private/cakey.pem -x509 -out cacert.pem -days 3650
Country Name (2 letter code) [GB]:CN
State or Province Name (full name) [Berkshire]:BEIJING
Locality Name (eg, city) [Newbury]:BEIJING
Organization Name (eg, company) [My Company Ltd]:SECCENTER
Organizational Unit Name (eg, section) []:tec
Common Name (eg, your name or your server's hostname) []:rootca.net.net
Email Address []:
創建鑰匙
[root@mail CA]# cd /etc/mail
[root@mail mail]# mkdir certs
[root@mail mail]# cd certs/
[root@mail certs]# openssl genrsa 1024 >sendmail.key
Generating RSA private key, 1024 bit long modulus
........++++++
...........................++++++
e is 65537 (0x10001)
請求文件
[root@mail certs]# openssl req -new -key sendmail.key -out sendmail.csr
Country Name (2 letter code) [GB]:CN
State or Province Name (full name) [Berkshire]:HENAN
Locality Name (eg, city) [Newbury]:ZHENGZHOU
Organization Name (eg, company) [My Company Ltd]:ZZDX
Organizational Unit Name (eg, section) []:tec
Common Name (eg, your name or your server's hostname) []:mail.bj.com
Email Address []:
證書
[root@mail certs]# openssl ca -in sendmail.csr -out sendmail.cert
Sign the certificate? [y/n]:y
1 out of 1 certificate requests certified, commit? [y/n]y
編輯sendmail.mc文件
[root@mail mail]# pwd
/etc/mail
[root@mail mail]# vim sendmail.mc
60 define(`confCACERT_PATH', `/etc/mail/certs')dnl
61 define(`confCACERT', `/etc/mail/certs/cacert.pem')dnl
62 define(`confSERVER_CERT', `/etc/mail/certs/sendmail.cert')dnl
63 define(`confSERVER_KEY', `/etc/mail/certs/sendmail.key')dnl
134 DAEMON_OPTIONS(`Port=smtps, Name=TLSMTA, M=s')dnl
設置鑰匙權限
[root@mail certs]# chmod 600 sendmail.key
拷貝cacert.pem到當前目錄下
[root@mail certs]# pwd
/etc/mail/certs
[root@mail certs]# cp /etc/pki/CA/cacert.pem ./
重啓sendmail服務
[root@mail mail]# service sendmail restart
Shutting down sm-client: [ OK ]
Shutting down sendmail: [ OK ]
Starting sendmail: [ OK ]
Starting sm-client: [ OK ]
查看一下
[root@mail certs]# telnet 127.0.0.1 25
Trying 127.0.0.1...
Connected to mail.bj.com (127.0.0.1).
Escape character is '^]'.
220 mail.bj.com ESMTP Sendmail 8.13.8/8.13.8; Fri, 23 Mar 2012 18:17:34 +0800
EHLO 127.0.0.1
250-mail.bj.com Hello mail.bj.com [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-STARTTLS
250-DELIVERBY
250 HELP
測試
北京外部郵件客戶機測試
用戶user1選上安全連接ssl
發送郵件和接受郵件時查看日誌，得到如下信息
[root@mail certs]# tail -f /var/log//maillog
Mar 23 19:08:08 mail sendmail[4219]: STARTTLS=server, relay=[192.168.2.3], version=TLSv1/SSLv3, verify=NO, cipher=RC4-MD5, bits=128/128
Mar 23 19:08:08 mail sendmail[4219]: q2NB88dj004219: from=<[email protected]>, size=1196, class=0, nrcpts=1, msgid=<B1896E86FE044F089D3715128ED98012@201106201040>, proto=SMTP, daemon=MTA, relay=[192.168.2.3]
Mar 23 19:08:09 mail sendmail[4220]: q2NB88dj004219: to=<[email protected]>, ctladdr=<[email protected]> (500/500), delay=00:00:01, xdelay=00:00:00, mailer=local, pri=31415, dsn=2.0.0, stat=Sent
Mar 23 19:08:44 mail dovecot: pop3-login: Login: user=<user1>, method=PLAIN, rip=::ffff:192.168.2.3, lip=::ffff:192.168.2.100
Mar 23 19:08:44 mail dovecot: POP3(user1): Disconnected: Logged out top=0/0, retr=1/1494, del=1/1, size=1477
[root@mail Server]# tshark -ni etho -R "tcp.dsport eq 110"
130.317087 192.168.2.3 -> 192.168.2.100 TCP 2446 > 110 [SYN] Seq=0 Win=65535 Len=0 MSS=1460 WS=3
130.317398 192.168.2.3 -> 192.168.2.100 TCP 2446 > 110 [ACK] Seq=1 Ack=1 Win=372296 Len=0
130.319027 192.168.2.3 -> 192.168.2.100 POP Request: USER user1
130.319511 192.168.2.3 -> 192.168.2.100 POP Request: PASS 123
130.406052 192.168.2.3 -> 192.168.2.100 POP Request: STAT
130.435409 192.168.2.3 -> 192.168.2.100 POP Request: LIST
130.439985 192.168.2.3 -> 192.168.2.100 POP Request: RETR 1
可以看出發送郵件時已經採用ssl進行加密，接受時還是採用明文pop3接受北抓包工具截獲到帳號和密碼
dovecot接收服務器實現安全接受（pops）
鑰匙請求文件
[root@mail certs]# mkdir -pv /etc/dovecot/certs
mkdir: created directory `/etc/dovecot'
mkdir: created directory `/etc/dovecot/certs'
[root@mail certs]# cd /etc/dovecot/certs/
[root@mail certs]# openssl genrsa 1024 >dovecot.key
Generating RSA private key, 1024 bit long modulus
..................++++++
......................++++++
e is 65537 (0x10001)
產生請求
[root@mail certs]# openssl req -new -key dovecot.key -out dovecot.csr
Country Name (2 letter code) [GB]:CN
State or Province Name (full name) [Berkshire]:HENAN
Locality Name (eg, city) [Newbury]:ZHENGZHOU
Organization Name (eg, company) [My Company Ltd]:ZZDX
Organizational Unit Name (eg, section) []:tec
Common Name (eg, your name or your server's hostname) []:pop3.bj.com
Email Address []:
請求證書
[root@mail certs]# openssl ca -in dovecot.csr -out dovecot.cert
Certificate Details:
Serial Number: 2 (0x2)
Validity
Not Before: Mar 23 13:04:19 2012 GMT
Not After : Mar 23 13:04:19 2013 GMT
Subject:
countryName = CN
stateOrProvinceName = HENAN
organizationName = ZZDX
organizationalUnitName = tec
commonName = pop3.bj.com
Sign the certificate? [y/n]:y
1 out of 1 certificate requests certified, commit? [y/n]y
修改權限
[root@mail certs]# chmod 600 *
編輯dovecot.conf文件
[root@mail certs]# vim /etc/dovecot.conf
21 protocols = imap pop3 imaps
94 ssl_cert_file = /etc/dovecot/certs/dovecot.cert
95 ssl_key_file = /etc/dovecot/certs/dovecot.key
重啓服務
[root@mail certs]# service dovecot restart
Stopping Dovecot Imap: [ OK ]
Starting Dovecot Imap: [ OK ]
查看運行端口
[root@mail certs]# netstat -tupln |grep dov
tcp 0 0 :::993 :::* LISTEN 4328/dovecot
tcp 0 0 :::110 :::* LISTEN 4328/dovecot
tcp 0 0 :::143 :::* LISTEN 4328/dovecot
測試接受郵件時是否加密
發送和接收郵件時查看到的日誌和抓取到的信息如下
[root@mail certs]# tail -f /var/log/maillog
Mar 23 21:52:23 mail sendmail[4377]: STARTTLS=server, relay=[192.168.2.3], version=TLSv1/SSLv3, verify=NO, cipher=RC4-MD5, bits=128/128
Mar 23 21:52:23 mail sendmail[4377]: q2NDqNw5004377: from=<[email protected]>, size=1179, class=0, nrcpts=1, msgid=<E198C88DE29A412893A4F7F067040E51@201106201040>, proto=SMTP, daemon=MTA, relay=[192.168.2.3]
Mar 23 21:52:23 mail sendmail[4384]: q2NDqNw5004377: to=<[email protected]>, ctladdr=<[email protected]> (501/501), delay=00:00:00, xdelay=00:00:00, mailer=local, pri=31398, dsn=2.0.0, stat=Sent
Mar 23 21:52:24 mail dovecot: imap-login: Login: user=<user2>, method=PLAIN, rip=::ffff:192.168.2.3, lip=::ffff:192.168.2.100, TLS
[root@mail Server]# tshark -ni eth0 -R "tcp.dstport eq 993"
345.571410 192.168.2.3 -> 192.168.2.100 TCP 3032 > 993 [ACK] Seq=292 Ack=836 Win=371464 Len=0
345.573477 192.168.2.3 -> 192.168.2.100 TLSv1 Application Data
345.574578 192.168.2.3 -> 192.168.2.100 TLSv1 Application Data
345.667520 192.168.2.3 -> 192.168.2.100 TLSv1 Application Data
345.673284 192.168.2.3 -> 192.168.2.100 TLSv1 Application Data
345.674900 192.168.2.3 -> 192.168.2.100 TLSv1 Application Data
可以看出郵件已成功發送和接收並沒有被截獲信息，實現了安全性的收發
郵件證書認證sasl
由於郵件服務器能夠讓所有用戶發送郵件，這並不安全，爲了解決這一現狀，我們採用sasl
是一種雙方通信的規則,是合法帳號纔可以發送
環境
[root@mail Server]# rpm -qa |grep sasl
cyrus-sasl-lib-2.1.22-5.el5
cyrus-sasl-2.1.22-5.el5
cyrus-sasl-devel-2.1.22-5.el5
cyrus-sasl-plain-2.1.22-5.el5
[root@mail Server]# chkconfig --list |grep sasl
saslauthd 0:off 1:off 2:off 3:off 4:off 5:off 6:off
啓動該服務，並設置爲開機自動啓動
[root@mail Server]# service saslauthd start
Starting saslauthd: [ OK ]
[root@mail Server]# chkconfig saslauthd on
編輯sendmail.mc文件
[root@mail Server]# vim /etc/mail/sendmail.mc
39 define(`confAUTH_OPTIONS', `A y')dnl
52 TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
53 define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
重啓服務
[root@mail Server]# service sendmail restart
Shutting down sm-client: [ OK ]
Shutting down sendmail: [ OK ]
Starting sendmail: [ OK ]
Starting sm-client: [ OK ]
查看
[root@mail Server]# telnet 127.0.0.1
Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Connection refused
telnet: Unable to connect to remote host: Connection refused
[root@mail Server]# telnet 127.0.0.1 25
Trying 127.0.0.1...
Connected to mail.bj.com (127.0.0.1).
Escape character is '^]'.
220 mail.bj.com ESMTP Sendmail 8.13.8/8.13.8; Fri, 23 Mar 2012 23:24:43 +0800
EHLO 127.0.0.1
250-mail.bj.com Hello mail.bj.com [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH LOGIN PLAIN
250-STARTTLS
250-DELIVERBY
250 HELP
強制驗證
[root@mail Server]# vim /etc/mail/sendmail.mc
116 DAEMON_OPTIONS(`Port=smtp,Addr=0.0.0.0, Name=MTA M=Ea')dnl
重啓服務
[root@mail Server]# service sendmail restart
測試
用客戶機user2給root用戶發送郵件，查看出的日誌如下
編碼帳號：
[root@mail ~]# echo -n "root" |openssl base64
cm9vdA==
[root@mail ~]# echo -n "redhat" |openssl base64
cmVkaGF0
[root@mail ~]# telnet 127.0.0.1 25
Trying 127.0.0.1...
Connected to mail.bj.com (127.0.0.1).
Escape character is '^]'.
220 mail.bj.com ESMTP Sendmail 8.13.8/8.13.8; Sat, 24 Mar 2012 00:25:25 +0800
EHLO 127.0.0.1
250-mail.bj.com Hello mail.bj.com [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH LOGIN PLAIN
250-STARTTLS
250-DELIVERBY
250 HELP
AUTH LOGIN cm9vdA==
334 UGFzc3dvcmQ6
cmVkaGF0
235 2.0.0 OK Authenticated
MAIL FROM:[email protected]
250 2.1.0 [email protected]... Sender ok
RCPT TO:[email protected]
250 2.1.5 [email protected]... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
111111111111111111
.
250 2.0.0 q2NGPPNd003329 Message accepted for delivery
[root@mail certs]# tail -f /var/log//maillog
Mar 23 23:39:38 mail dovecot: imap-login: Login: user=<user2>, method=PLAIN, rip=::ffff:192.168.2.3, lip=::ffff:192.168.2.100, TLS
Mar 23 23:40:15 mail sendmail[4768]: STARTTLS=server, relay=[192.168.2.3], version=TLSv1/SSLv3, verify=NO, cipher=RC4-MD5, bits=128/128
Mar 23 23:40:15 mail sendmail[4768]: AUTH=server, relay=[192.168.2.3], authid=user2, mech=LOGIN, bits=0
Mar 23 23:40:15 mail sendmail[4768]: q2NFeFoM004768: from=<[email protected]>, size=1199, class=0, nrcpts=1, msgid=<81A4F08C96004DC891735E1C529BFAA1@201106201040>, proto=ESMTP, daemon=MTA M=Ea, relay=[192.168.2.3]
Mar 23 23:40:15 mail sendmail[4772]: q2NFeFoM004768: to=<[email protected]>, ctladdr=<[email protected]> (501/501), delay=00:00:00, xdelay=00:00:00, mailer=local, pri=31442, dsn=2.0.0, stat=Sent
Mar 23 23:40:15 mail dovecot: imap-login: Login: user=<user2>, method=PLAIN, rip=::ffff:192.168.2.3, lip=::ffff:192.168.2.100, TLS
sendmail-doc-8.13.8-2.el5.i386.rpm