and with any additional parameters or verbs similarly marked. SMTP commands are case-insensitive. They are presented here in capitalized form for emphasis only. An SMTP server that requires a specific capitalization method is a violation of the standard. 8BITMIME At least the following servers advertise the 8BITMIME extension: Apache James (since 2.3.0a1) Citadel (since 7.30) Courier Mail Server Gmail IceWarp IIS SMTP Service Kerio Connect Lotus Domino Microsoft Exchange Server (as of Exchange Server 2000) Novell GroupWise OpenSMTPD Oracle Communications Messaging Server Postfix Sendmail (since 6.57) The following servers can be configured to advertise 8BITMIME, but do not perform conversion of 8-bit data to 7-bit when connecting to non-8BITMIME relays: Exim and qmail do not translate eight-bit messages to seven-bit when making an attempt to relay 8-bit data to non-8BITMIME peers, as is required by the RFC. This does not cause problems in practice, since virtually all modern mail relays are 8-bit clean. Microsoft Exchange Server 2003 advertises 8BITMIME by default, but relaying to a non-8BITMIME peer results in a bounce. This is allowed by RFC 6152 section 3. SMTP-AUTH The SMTP-AUTH extension provides an access control mechanism. It consists of an authentication step through which the client effectively logs into the mail server during the process of sending mail. Servers that support SMTP-AUTH can usually be configured to require clients to use this extension, ensuring the true identity of the sender is known. The SMTP-AUTH extension is defined in . SMTP-AUTH can be used to allow legitimate users to relay mail while denying relay service to unauthorized users, such as spammers. It does not necessarily guarantee the authenticity of either the SMTP envelope sender or the "From:" header. For example, spoofing, in which one sender masquerades as someone else, is still possible with SMTP-AUTH unless the server is configured to limit message from-addresses to addresses this AUTHed user is authorized for. The SMTP-AUTH extension also allows one mail server to indicate to another that the sender has been authenticated when relaying mail. In general this requires the recipient server to trust the sending server, meaning that this aspect of SMTP-AUTH is rarely used on the Internet. SMTPUTF8 Supporting servers include: Postfix (version 3.0 and later) Momentum (versions 4.1 and 3.6.5, and later) Sendmail (experimental support in 8.17.1) Exim (experimental as of the 4.86 release, quite mature in 4.96) CommuniGate Pro as of version 6.2.2 Courier-MTA as of version 1.0