Are email addresses case sensitive?

From RFC 5321, section 2.3.11: The standard mailbox naming convention is defined to be “local-part@domain”; contemporary usage permits a much broader set of applications than simple “user names”. Consequently, and due to a long history of problems when intermediate hosts have attempted to optimize transport by modifying them, the local-part MUST be interpreted and assigned … Read more

What is the behavior difference between return-path, reply-to and from?

Let’s start with a simple example. Let’s say you have an email list, that is going to send out the following RFC2822 content. From: <coolstuff@mymailinglist.example> To: <you@example.com> Subject: Super simple email Reply-To: <coolstuff-threadId=123@mymailinglist.example> This is a very simple body. Now, let’s say you are going to send it from a mailing list, that implements VERP … Read more

Data URI scheme and Internet Explorer 9 Errors

Data URIs cannot be used for navigation, for scripting, or to populate frame or iframe elements in IE. According to http://msdn.microsoft.com/en-us/library/cc848897%28v=vs.85%29.aspx: Data URIs are supported only for the following elements and/or attributes. object (images only) img input type=image link CSS declarations that accept a URL, such as background, backgroundImage, and so on. Data URIs can … Read more

Why do HTTP servers forbid underscores in HTTP header names

They are not forbidden, it’s CGI legacy. See “Missing (disappearing) HTTP Headers”. If you do not explicitly set underscores_in_headers on;, nginx will silently drop HTTP headers with underscores (which are perfectly valid according to the HTTP standard). This is done in order to prevent ambiguities when mapping headers to CGI variables, as both dashes and … Read more

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