如果squirremail未邮件开启smtp认证：

用squirrelmail发送邮件时出现如下提示:

Message not sent. Server replied:

Transaction failed

554 5.7.1 <52********@qq.com>: Relay access denied

进入 squirremail目录  /var/www/html/webmail

config/conf.pl

Main Menu --

1.  Organization Preferences

2.  Server Settings

3.  Folder Defaults

4.  General Options

5.  Themes

6.  Address Books

7.  Message of the Day (MOTD)

8.  Plugins

9.  Database

10. Languages

按照提示选择2

Server Settings

General

-------

1.  Domain                 : localhost.localdomain

2.  Invert Time            : false

3.  Sendmail or SMTP       : SMTP

A.  Update IMAP Settings   : localhost:143 (dovecot)

B.  Update SMTP Settings   : 127.0.0.1:25

R   Return to Main Menu

C   Turn color on

S   Save data

Q   Quit

选择B

Server Settings

General

-------

1.  Domain                 : localhost.localdomain

2.  Invert Time            : false

3.  Sendmail or SMTP       : SMTP

SMTP Settings

-------------

4.   SMTP Server           : 127.0.0.1

5.   SMTP Port             : 25

6.   POP before SMTP       : false

7.   SMTP Authentication   : none          将这个改为login

8.   Secure SMTP (TLS)     : false

9.   Header encryption key :

选择7

Command >> 7

*** YOUR SMTP SERVER MUST SUPPORT THE MECHANISM YOU CHOOSE HERE ***

If you don't understand or are unsure, you probably want "none"

none, login, cram-md5, or digest-md5 [none]: login      将none改为login

SMTP authentication uses IMAP username and password by default.

Would you like to use other login and password for all SquirrelMail

SMTP connections? [y/N]:N

R   Return to Main Menu

C   Turn color on

S   Save data

Q   Quit

保存退出后再使用squirrelmail发送邮件就可以了。