Technical
New to the email queue? We’ve got you covered. This tutorial will show you how how to view, flush, and purge queued mail in Postfix. The post How to Flush the Mail Queue in Postfix appeared first on SendGrid.
Return-path is a hidden email header that indicates where and how bounced emails will be processed and is used for collecting and processing bounced messages. The post What Is Return-Path Header (And Why It Matters) appeared first on SendGrid.
When we’re looking at the technical details of email addresses there are two quite different contexts we talk about. One is an “821 address” or “5321 address”. This is the email address as it’s used by the SMTP protocol, as part of the “MAIL FROM: ” or “RCPT TO: ” commands sent to the mailserver. It’s defined in RFC 821, now updated by RFC 5321, hence the name. If someone mentions the “envelope” or they’re talking about “bounce addresses”, this is the sort they mean. We’re not talking about them in this post. The other is an “822 address” or a “5322 address’. They’re the ones the recipient sees in the To: or From: headers. They’re named after their RFC, RFC 5322. This is the sort of email address most folks mean by default, unless they’re explicitly talking about the envelope of an email, but if someone describes an email
It looks like Microsoft are getting pickier about email address syntax, rejecting mail that uses illegal address formats. That might be what’s causing that “550 5.6.0 CAT.InvalidContent.Exception: DataSourceOperationException, proxyAddress: prefix not supported – ; cannot handle content of message” rejection. Why do we care? It’s good to send syntactically valid email in a warm fuzzies sort of way – it shows we know what we’re doing, and aren’t dodgy spamware – but it’s increasingly important to delivery as mailbox providers are tightening up on their syntax checks. But why are mailbox providers doing that? One reason is that authentication tech like DKIM and DMARC is built around them only being applied to email. Not to messages that kinda look like email. There are ways to bypass DKIM protections by sending invalid messages. As one example, if you send multiple copies of the From: header with different values a DKIM checker
Over the past decade, Twilio SendGrid has embraced Transport Layer Security (TLS) encryption as a way to protect outbound emails as these travel between servers. In a digital world rife with cyberattacks, implementing true end-to-end email encryption for sensitive emails has become increasingly necessary. But what exactly does this mean? This post provides an overview […] The post Paranoid Email: End-to-End Encryption Primer appeared first on SendGrid.
Here’s how SendGrid breaks down the differences between webhooks and APIs and how you can start using webhooks. The post Webhook vs API: What’s the Difference Between Them? appeared first on SendGrid.
SMTP servers send response codes that indicate what has happened to your messages. Here’s what a handful of them mean. The post SMTP Error Codes: What Do These Server Responses Mean? appeared first on SendGrid.
Spam traps are a common tool for companies wondering how to detect spam. Here we explain what spam traps are and how to identify and avoid them. The post Spam Traps: What They Are & How to Avoid Them appeared first on SendGrid.
Learn more about the protocol encryption command, StartTLS, and how email is encrypted when sending via SMTP. The post What is StartTLS? appeared first on SendGrid.
What is an SMTP, how do SMTP servers send email, and how does Twilio SendGrid fit in? Learn more about the breakdown of the basics of SMTP servers. The post SMTP: Servers and Sending Emails appeared first on SendGrid.