簡介
本文說明如何解決郵件安全裝置(ESA)上的傳送問題。
必要條件
需求
思科建議您瞭解以下主題：
- 通過郵件日誌或郵件跟蹤跟蹤出站郵件
- 訪問ESA的CLI
採用元件
本文檔中的資訊基於AsyncOS for Email Security。
本文中的資訊是根據特定實驗室環境內的裝置所建立。文中使用到的所有裝置皆從已清除（預設）的組態來啟動。如果您的網路運作中，請確保您瞭解任何指令可能造成的影響。
背景資訊
ESA可以接收郵件，但郵件似乎沒有到達目的地。如何確定ESA不向特定域或特定域傳送郵件的原因？ESA無法傳送消息的原因有很多，本文重點介紹遠端域的調試問題。
疑難排解步驟
tophosts命令
要獲取有關電子郵件隊列的即時資訊並確定特定收件人主機是否存在傳遞問題（如隊列增加），請使用 tophosts 指令。其 tophosts 命令返回隊列中前20個接收主機的清單。該清單可以按許多不同的統計資訊排序，包括活動收件人、傳出連線、已傳遞收件人、軟退回事件和硬退回收件人。
運行 tophosts 命令並按活動收件人排序，以便檢視哪些主機具有最大的傳送隊列。
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
運行 hoststatus 命令檢查已使用的MX記錄和狀態。如果Host up/down:未知或關閉，請嘗試使用SMTPING工具向該主機傳送消息（如下圖所示），然後檢視狀態是否更改。主機狀態顯示上次嘗試傳送的狀態。
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
運行 nslookup 命令驗證收件人域的MX記錄是否有效。
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
運行 dnsflush 命令，如果為了提取新的MX記錄而更正了DNS記錄。
mail.example.com> dnsflush
Are you sure you want to clear out the DNS cache? [N]> Y
SMTPING工具
運行SMTPING工具進行連通性測試並傳送測試消息。
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
運行 delivernow 命令並強制ESA重新嘗試向所有主機或特定主機傳送資料。
mail.example.com> delivernow
Please choose an option for scheduling immediate delivery.
1. By recipient domain
2. All messages
[1]> 2
相關資訊
意見