简介
本文档介绍由于思科邮件安全设备(ESA)上的邮件头过大而被拒绝和退回的邮件。
具有“552 #5.3.4邮件报头大小超过限制”的退回邮件
当主机尝试发送具有较大报头的邮件时，ESA可能会拒绝该邮件。最终用户可能会看到以下错误消息之一：
"552 #5.3.4 message header size exceeds limit"
"500 #5.5.1 command not recognized"
"421 Exceeded bad SMTP command limit"
在其他情况下，主机可能会继续重试同一消息。
邮件报头不能超过1000行。当报头长度超过1000行时，ESA会将“552 #5.3.4 message header size exceeds limit”消息发送到发送主机。
某些主机可能会忽略此消息并继续发送数据。ESA将数据解释为SMTP命令，并返回每行“500 #5.5.1 command not recognized”。
在超过4个错误SMTP命令的限制后，ESA返回消息“421已超过错误SMTP命令限制”，并丢弃连接。
只能在CLI上更改此设置：
myesa.local> listenerconfig
Currently configured listeners:
1. listener_myesa.local (on Management, 192.168.0.199) SMTP TCP Port 25 Public
Choose the operation you want to perform:
- NEW - Create a new listener.
- EDIT - Modify a listener.
- DELETE - Remove a listener.
- SETUP - Change global settings.
[]> setup
Enter the global limit for concurrent connections to be allowed across
all listeners.
[50]>
Listener istener_myesa.local Policy $TRUSTED max concurrency value of 300
will be limited to 50 by this concurrency setting.
Enter the global limit for concurrent TLS connections to be allowed across
all listeners.
[100]>
Concurrent TLS connections value of 100 will be limited to 50 by the global
limit for concurrent connections.
Enter the maximum number of message header lines. 0 indicates no limit.
[1000]>
Enter the rate at which injection control counters are reset.
[1h]>
Enter the timeout for unsuccessful inbound connections.
[5m]>
Enter the maximum connection time for inbound connections.
[15m]>
What hostname should Received: headers be stamped with?
1. The hostname of the Virtual Gateway(tm) used for delivering the message
2. The hostname of the interface the message is received on
[2]>
The system will always add a Message-ID header to outgoing messages that don't
already have one. Would you like to do the same for incoming messages? (Not
recommended.) [N]>
By default connections with a HAT REJECT policy will be closed with a banner
message at the start of the SMTP conversation. Would you like to do the rejection
at the message recipient level instead for more
detailed logging of rejected mail? [N]>
如果进行了任何更改或更新，请返回主CLI提示符并运行commit以保存和实施更改。
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