简介
本文档介绍如何解决邮件安全设备(ESA)上的传输问题。
先决条件
要求
Cisco 建议您了解以下主题：
- 通过邮件日志或邮件跟踪来跟踪出站邮件
- 访问ESA的CLI
使用的组件
本文档中的信息基于AsyncOS for Email Security。
本文档中的信息都是基于特定实验室环境中的设备编写的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您的网络处于活动状态，请确保您了解所有命令的潜在影响。
背景信息
ESA可以接收邮件，但邮件似乎没有到达目的地。如何确定ESA不向一个或多个特定域发送邮件的原因？ESA无法发送消息的原因有很多。本文重点介绍远程域的调试问题。
故障排除步骤
tophosts命令
要获取有关电子邮件队列的即时信息并确定特定收件人主机是否出现传递问题（例如队列增加），请使用 tophosts 命令。此 tophosts 命令返回队列中前20个收件人主机的列表。列表可以按许多不同的统计信息排序，包括活动收件人、传出连接、已传送收件人、软退回事件和硬退回收件人。
运行 tophosts 命令并按活动收件人排序，以便查看哪些主机具有最大的传送队列。
mail.example.com > tophosts
Sort results by:
1. Active Recipients
2. Connections Out
3. Delivered Recipients
4. Hard Bounced Recipients
5. Soft Bounced Events
[1]>
hoststatus命令
运行 hoststatus 命令，检查使用的MX记录和状态。如果Host up/down:为unknown或down，请尝试使用SMTPING工具向该主机发送消息（如下图所示），然后查看状态是否更改。主机状态显示上次尝试传送时的状态。
mail.example.com> hoststatus cisco.com
Host mail status for: 'cisco.com'
Status as of: Wed Sep 17 11:49:42 2014 CEST
Host up/down: unknown
Counters:
Queue
Soft Bounced Events 0
Completion
Completed Recipients 0
Hard Bounced Recipients 0
DNS Hard Bounces 0
5XX Hard Bounces 0
Filter Hard Bounces 0
Expired Hard Bounces 0
Other Hard Bounces 0
Delivered Recipients 0
Deleted Recipients 0
Gauges:
Queue
Active Recipients 0
Unattempted Recipients 0
Attempted Recipients 0
Connections
Current Outbound Connections 0
Pending Outbound Connections 0
Oldest Message No Messages
Last Activity Wed Sep 17 11:49:39 2014 CEST
Ordered IP addresses: (expiring at Tue Mar 04 08:16:06 2014 CET)
Preference IPs
10 172.31.147.230:25
MX Records:
Preference TTL Hostname
10 1d12s alln-mx-01.cisco.com
nslookup命令
运行 nslookup 命令，以验证收件人域的MX记录是否有效。
mail.example.com> nslookup
Please enter the host or IP address to resolve.
[]> cisco.com
Choose the query type:
1. A the host's IP address
2. AAAA the host's IPv6 address
3. CNAME the canonical name for an alias
4. MX the mail exchanger
5. NS the name server for the named zone
6. PTR the hostname if the query is an Internet address,
otherwise the pointer to other information
7. SOA the domain's "start-of-authority" information
8. TXT the text information
[1]> 4
MX=rcdn-mx-01.cisco.com PREF=20 TTL=1d
MX=aer-mx-01.cisco.com PREF=30 TTL=1d
MX=alln-mx-01.cisco.com PREF=10 TTL=1d
dnsflush命令
运行 dnsflush 命令，如果已更正DNS记录以提取新的MX记录。
mail.example.com> dnsflush
Are you sure you want to clear out the DNS cache? [N]> Y
SMTPING工具
运行SMTPING工具进行连通性测试并发送测试消息。
mail.example.com> diagnostic
Choose the operation you want to perform:
- RAID - Disk Verify Utility.
- DISK_USAGE - Check Disk Usage.
- NETWORK - Network Utilities.
- REPORTING - Reporting Utilities.
- TRACKING - Tracking Utilities.
- RELOAD - Reset configuration to the initial manufacturer values.
[]> network
Choose the operation you want to perform:
- FLUSH - Flush all network related caches.
- ARPSHOW - Show system ARP cache.
- NDPSHOW - Show system NDP cache.
- SMTPPING - Test a remote SMTP server.
- TCPDUMP - Dump ethernet packets.
[]> smtpping
Enter the hostname or IP address of the SMTP server:
[mail.example.com]> cisco.com
The domain you entered has MX records.
Would you like to select an MX host to test instead? [Y]>
Select an MX host to test.
1. aer-mx-01.cisco.com
2. alln-mx-01.cisco.com
3. rcdn-mx-01.cisco.com
[1]> 2
Select a network interface to use for the test.
1. Management
2. auto
[2]>
Do you want to type in a test message to send? If not, the connection can be
tested but no email can be sent. [N]> Y
Enter the From e-mail address:
[from@example.com]>
Enter the To e-mail address:
[to@example.com]> postmaster@cisco.com
Enter the Subject:
[Test Message]>
Enter the Body of the message one line at a time. End with a "." on a line by itself.
Test only
.
Starting SMTP test of host alln-mx-01.cisco.com.
Resolved 'alln-mx-01.cisco.com' to 172.31.147.230.
Connection to 172.31.147.230 succeeded.
Command EHLO succeeded
Command MAIL FROM succeeded.
Command RCPT TO succeeded.
Command DATA succeeded.
Mesage body accepted.
Test complete. Total time elapsed 1.48 seconds
Choose the operation you want to perform:
- FLUSH - Flush all network related caches.
- ARPSHOW - Show system ARP cache.
- NDPSHOW - Show system NDP cache.
- SMTPPING - Test a remote SMTP server.
- TCPDUMP - Dump ethernet packets
delivernow命令
运行 delivernow 命令并强制ESA重新尝试向所有主机或特定主机发送邮件。
mail.example.com> delivernow
Please choose an option for scheduling immediate delivery.
1. By recipient domain
2. All messages
[1]> 2
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