WSM User Guide - WatchGuard Technologies

Configuring the SMTP Proxyand 8-bit MIME. 8-bit MIME content (for example, MIME attachments) is encoded with standardalgorithms (Base64 or quote-printable encoding) to enable them to be sent through 7-bit e-mail systems. Encoding can increase the length of files by as much as one third. To allowmessages as large as 1000 bytes, you must set this field to a minimum of 1334 bytes to makesure all e-mail gets through. The default value is 3,000,000 bytes (3 million bytes).Maximum e-mail line lengthWith the Set the maximum e-mail line length to check box, you can set the maximum linelength for lines in an SMTP message. Very long line lengths can cause buffer overflows on somee-mail systems. Most e-mail clients and systems send short line lengths, but some web-based e-mail systems send very long lines. The default value is 1024.Hide E-mail ServerSelect the Message ID and Server Replies check boxes to replace MIME boundary and SMTPgreeting strings in e-mail messages. These are used by hackers to identify the SMTP servervendor and version.If you have an e-mail server and use the SMTP-Incoming proxy action, you can have the SMTPproxy replace the domain shown in your SMTP server banner with a domain name you select.To do this, select the Rewrite Banner Domain check box and type the domain name you wantto use in your banner in the text box that appears. For this to occur, you must also have theServer Replies check box selected.If you use the SMTP-Outgoing proxy action, you can have the SMTP proxy replace the domainshown in the HELO or EHLO greetings. A HELO or EHLO greeting is the first part of an SMTPtransaction, when your e-mail server announces itself to a receiving e-mail server. To do this,select the Rewrite HELO Domain check box and type the domain name you want to use inyour HELO or EHLO greeting in the text box that appears.Send a log messageSelect the Send a log message check box to send a log message for each connection requestthrough SMTP. For Historical Reports to create accurate reports on SMTP traffic, you must selectthis check box.Greeting rulesThe proxy examines the initial HELO/EHLO responses during the SMTP session initialization. Thedefault rules for the SMTP-Incoming proxy action make sure that packets with greetings thatare too long, or include characters that are not correct or expected, are denied.Configuring ESMTP parametersYou use the ESMTP Settings fields to set the filtering for ESMTP content. Although SMTP is widelyaccepted and widely used, some parts of the Internet community have found a need to extend SMTP to168 WatchGuard System Manager