我在一台 ubuntu 8.04 机器上运行 dovecot imap 服务器（我知道这台机器很旧，但近期不可能升级）。无论如何，一切都运行顺利，直到前几天我重新启动服务器，现在我们无法通过该服务器发送电子邮件。电子邮件客户端都是 Windows 机器上的 Mozilla Thunderbird。电子邮件可以很好地下载到 Thunderbird 中，但当我们尝试发送电子邮件时，我们会收到一条消息，说login to server mail.mydomain当我单击它时enter new passord，它总是失败并显示login to server mail.mydomain弹出窗口。当我单击此弹出窗口上的取消时，我收到消息：
邮件发送失败。由于未知原因，无法使用 SMTP 服务器 mail.mailserverdomain 发送邮件。请确认您的 SMTP 服务器设置正确并重试，或联系您的网络管理员。
我查看了一下/var/log/mail.log，发现了这个（这个是 windows 机器网络上的 thunderbird 客户端）：
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: warning: database /etc/postfix/client_restrictions.db is older than source file /etc/postfix/client_restrictions
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: connect from my.windows.machine.gateway[xxx.xxx.xxx.xxx]
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: setting up TLS connection from my.windows.machine.gateway[xxx.xxx.xxx.xxx]
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: Anonymous TLS connection established from my.windows.machine.gateway[xxx.xxx.xxx.xxx]: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: warning: SASL authentication problem: unable to open Berkeley db /etc/sasldb2: No such file or directory
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: warning: SASL authentication problem: unable to open Berkeley db /etc/sasldb2: No such file or directory
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: warning: SASL authentication failure: no secret in database
Oct 15 16:29:20 mailserverdomain postfix/smtpd[1918]: warning: my.windows.machine.gateway[xxx.xxx.xxx.xxx]: SASL CRAM-MD5 authentication failed: authentication failure
Oct 15 16:29:23 mailserverdomain postfix/pickup[1622]: 6AFEA12A9C2: uid=33 from=<mythunderbirdusername@mailserverdomain>
Oct 15 16:29:23 mailserverdomain postfix/cleanup[1924]: 6AFEA12A9C2: message-id=<5d030c180944e864204de7263d12c5ba@mailserverdomain>
Oct 15 16:29:23 mailserverdomain postfix/qmgr[22190]: 6AFEA12A9C2: from=<mythunderbirdusername@mailserverdomain>, size=1683, nrcpt=1 (queue active)
Oct 15 16:29:24 mailserverdomain postfix/smtpd[1918]: disconnect from my.windows.machine.gateway[xxx.xxx.xxx.xxx]
Oct 15 16:29:25 mailserverdomain postfix/smtp[1926]: Host offered STARTTLS: [todomain]
Oct 15 16:29:28 mailserverdomain postfix/smtp[1926]: 6AFEA12A9C2: to=<to_username@todomain>, relay=todomain[xxx.xxx.xxx.xxx]:25, delay=5.4, delays=0.12/0/1.7/3.6, dsn=2.6.0, status=sent (250 2.6.0 <5d030c180944e864204de7263d12c5ba@mailserverdomain> [InternalId=9002251459330, Hostname=tosubdomain.todomain] Queued mail for delivery)
Oct 15 16:29:28 mailserverdomain postfix/qmgr[22190]: 6AFEA12A9C2: removed
Oct 15 16:30:06 mailserverdomain postfix/pickup[1622]: 17F5512A9C2: uid=0 from=<mythunderbirdusername@mailserverdomain>
Oct 15 16:30:06 mailserverdomain postfix/cleanup[1924]: 17F5512A9C2: message-id=<[email protected]>
Oct 15 16:30:06 mailserverdomain postfix/qmgr[22190]: 17F5512A9C2: from=<mythunderbirdusername@mailserverdomain>, size=35784, nrcpt=2 (queue active)
Oct 15 16:30:07 mailserverdomain postfix/smtp[1926]: Host offered STARTTLS: [todomain]
Oct 15 16:30:08 mailserverdomain postfix/smtp[1946]: Host offered STARTTLS: [otherdomain]
Oct 15 16:30:10 mailserverdomain postfix/smtp[1946]: 17F5512A9C2: to=<another_username@otherdomain (i'm not sure why this is here?)>, relay=otherhost[xxx.xxx.xxx.xxx]:25, delay=4.7, delays=0.12/0.01/2.4/2.2, dsn=2.0.0, status=sent (250 ok: Message 137375323 accepted)
Oct 15 16:30:14 mailserverdomain postfix/smtp[1926]: 17F5512A9C2: to=<to_username@todomain>, relay=todomain[xxx.xxx.xxx.xxx]:25, delay=8.8, delays=0.12/0/1.5/7.2, dsn=2.6.0, status=sent (250 2.6.0 <[email protected]> [InternalId=9174050144279, Hostname=tosubdomain.todomain] Queued mail for delivery)
Oct 15 16:30:14 mailserverdomain postfix/qmgr[22190]: 17F5512A9C2: removed
该文件/etc/default/saslauthd如下所示：
#
# Settings for saslauthd daemon
# Please read /usr/share/doc/sasl2-bin/README.Debian for details.
#
# Should saslauthd run automatically on startup? (default: no)
START=yes
PWDIR="/var/spool/postfix/var/run/saslauthd"
PARAMS="-m ${PWDIR}"
PIDFILE="${PWDIR}/saslauthd.pid"
# Description of this saslauthd instance. Recommended.
# (suggestion: SASL Authentication Daemon)
DESC="SASL Authentication Daemon"
# Short name of this saslauthd instance. Strongly recommended.
# (suggestion: saslauthd)
NAME="saslauthd"
# Which authentication mechanisms should saslauthd use? (default: pam)
#
# Available options in this Debian package:
# getpwent -- use the getpwent() library function
# kerberos5 -- use Kerberos 5
# pam -- use PAM
# rimap -- use a remote IMAP server
# shadow -- use the local shadow password file
# sasldb -- use the local sasldb database file
# ldap -- use LDAP (configuration is in /etc/saslauthd.conf)
#
# Only one option may be used at a time. See the saslauthd man page
# for more information.
#
# Example: MECHANISMS="pam"
MECHANISMS="pam"
# Additional options for this mechanism. (default: none)
# See the saslauthd man page for information about mech-specific options.
MECH_OPTIONS=""
# How many saslauthd processes should we run? (default: 5)
# A value of 0 will fork a new process for each connection.
THREADS=5
# Other options (default: -c -m /var/run/saslauthd)
# Note: You MUST specify the -m option or saslauthd won't run!
#
# See /usr/share/doc/sasl2-bin/README.Debian for Debian-specific information.
# See the saslauthd man page for general information about these options.
#
# Example for postfix users: "-c -m /var/spool/postfix/var/run/saslauthd"
OPTIONS="-c -m /var/spool/postfix/var/run/saslauthd"
有什么办法可以解决这个问题吗？我拥有服务器的完全访问权限，因此如果需要，我可以提供日志中的信息。