Strict Syntax Parameters

There are two parameters configured in that require strict adherence to Internet email standards. Enable the smtpd_helo_required parameter to require that SMTP clients start the conversation with the HELO/EHLO verb, as described in the SMTP RFC. By default Postfix is rather lenient with clients that do not follow the protocol exactly. If you specify smtpd_helo_required = yes, and a client skips this step, Postfix rejects the message. The RFC also specifies exactly how envelope addresses should be formatted. Normally, Postfix accepts nearly any envelope address that it can make sense of, but if you specify strict_rfc821_envelopes = yes, Postfix rejects messages from clients that do not send correctly formatted addresses.

In actual practice, it's probably a good idea to require HELO because most clients at least follow the basic steps of the protocol. On the other hand, there are a number of clients that don't get address formatting correct. Being too strict here might lose legitimate messages.



Postfix Architecture

General Configuration and Administration

Queue Management

Email and DNS

Local Delivery and POP/IMAP

Hosting Multiple Domains

Mail Relaying

Mailing Lists

Blocking Unsolicited Bulk Email

SASL Authentication

Transport Layer Security

Content Filtering

External Databases

Appendix A. Configuration Parameters

Appendix B. Postfix Commands

Appendix C. Compiling and Installing Postfix

Appendix D. Frequently Asked Questions

Postfix(c) The Definitive Guide
Postfix: The Definitive Guide
ISBN: 0596002122
EAN: 2147483647
Year: 2006
Pages: 130
Authors: Kyle Dent D. © 2008-2020.
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