The OSI Seven Layer Model


In the 1970s, while the early drafts of the Internet were being developed, a competing model for networking was being put together by the ISO (International Organization for Standardization). The OSI (Open Systems Interconnection) Model broke the work needed to implement a distributed network service into seven separate layers of abstraction, from the physical infrastructure at layer one all the way up to the application…

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Using Reply-To:


Yesterday I learned that some ESPs don’t support the reply to: address. I asked around to discover which ESPs did. Here’s what I learned. ESPs that support reply-to: ActiveCampaignAmazonSESConstantContactCampaign MonitorCordialDelivraDoListEloquaEmmaEpsilonGetResponseHubSpotiContactListrakMailkitMailUpMarketoN6PardotwordResponsysSailthruSFMCSharpspringTwilio / SendGridZeta Global Thanks to all the colleagues who answered my question.

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Some notes on some of the different protocols used for authentication and authentication-adjacent things in email. Some of this is oral history, and some of it may be contradicted by later or more public historical revision. SPF Associates an email with a domain that takes responsibility for it. Originally Sender Permitted From, now Sender Policy Framework. It allows a domain owner to announce which IP…

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