Watchguard Firebox X15 User Manual page 157

SMTP proxy: Proxy limits
On the SMTP Settings tab, you can adjust timeout, email size, and line length limits. This stops the SMTP proxy
from using too many network resources and can prevent some types of attacks. You can also customize the
deny message that users see when an email message is blocked by the SMTP proxy.
Timeout
Set the length of time an incoming SMTP connection can idle before the SMTP proxy closes the
connection.
Maximum email size
By default, the SMTP proxy does not restrict email by size (this field is set to zero). Use this setting if
you want to set the maximum length of incoming SMTP messages. Most email is sent as 7-bit ASCII
text. Encoding can increase the length of files by as much as one-third. To allow messages as large as
1MB (1024Kb) you must set this field to a minimum of 1.4MB (1400Kb) to make sure all email
messages and their attachments get through.
Maximum line length
Set the maximum line length for lines in an SMTP message. Very long line lengths can cause buffer
overflows on some email systems. Most email clients and systems send short line lengths, but some
web-based email systems send very long lines.
User Guide
Proxy Settings
145