Category: SMTP & Infrastructure
SMTP & InfrastructureTransactional email has fundamentally different infrastructure requirements from marketing campaigns — it needs to be fast, reliable, and completely isolated from anything that could drag down its deliverability. This guide covers the architecture decisions that matter: queue design, authentication, suppression lists, monitoring, and how to test before you go live.
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SMTP & InfrastructureA misconfigured SMTP server can be exploited as an open relay, used to send spam from your domain, or damage your sending reputation in ways that take weeks to repair. This practical hardening checklist covers open relay prevention, TLS enforcement, rate limiting, authentication requirements, and the ongoing monitoring that keeps your mail server secure long-term.
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SMTP & InfrastructureSMTP ports 25, 465, 587, and 2525 all do different things — and using the wrong one is a surprisingly common cause of email delivery failures. Here's exactly what each port is for and which one your setup should be using.
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SMTP & InfrastructureSMTP authentication failures stop outgoing email cold. Whether you're seeing a 535 invalid credentials error, a 530 STARTTLS requirement, or a 454 temporary failure, this guide covers what each error means and exactly how to fix it.
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SMTP & InfrastructureSMTP relay monitoring goes beyond server health metrics. Delivery rate by provider, queue depth and age, SMTP response code distribution, and authentication pass rate are the signals that tell you whether messages are actually reaching recipients — before a customer has to tell you they're not.
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SMTP & InfrastructureEmail APIs let developers send transactional email with an HTTP request — but deliverability, error handling, domain authentication, and webhook processing all need to be wired up correctly for it to work reliably at scale.
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SMTP & InfrastructureA mail server connected to the internet is a high-value target for open relay abuse, spam injection, and phishing attacks. This checklist covers SMTP hardening essentials — from closing open relays and enforcing TLS to rate limiting, authentication records, and monitoring.
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SMTP & InfrastructureA backed-up SMTP queue means delayed password resets, missed delivery windows, and throttling from major ISPs. Here's how to tune your queue configuration so mail moves reliably under load.
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SMTP & InfrastructureMixing marketing and transactional email on the same infrastructure means a spam complaint spike from a newsletter can delay password resets and order confirmations. Here's why separation matters and how to set it up properly.
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