All articles · Page 2
Sending mail through a relay: Checking TLS and authentication
A one-pager for Application Managers whose applications send mail through a relay: Which three application settings matter (port, TLS mode, authentication), what the options are called in common environments, and how a single test email’s Received header proves that the connection is actually encrypted and authenticated.
SMTP Load Testing with Numbered Recipients: Send Every Email Traceably
A load test is only as good as its evaluation. With the -N option, smtp-source numbers every email via the recipient address without sacrificing throughput. Learn how to structure the run, how many sessions make sense, and how to automatically find missing numbers.
smtp-source without installing Postfix: Extract load-testing tools from the RPM
smtp-source and smtp-sink are part of Postfix, but they also run without an installed mail server. Learn how to extract the two tools from the package on RHEL, why running them from /tmp can fail because of the noexec mount option, and which libraries need to be included.
Up to 10 Million Free Tokens per Day: Using OpenAI’s Data-Sharing Program with Cost Guardrails
OpenAI gives organizations that share their API traffic for training a daily free allowance: depending on the tier, up to 10 million tokens. With prepaid credit, project limits, and a token budget in the code, usage remains free indefinitely.
Analyze Email Headers Without Uploading the Email: Locally in the Browser Instead of in a Web Tool
Email headers contain internal hostnames, IP addresses, and personal data. Anyone who pastes them into an online tool sends this information to a third-party server. Why analysis does not need a server and what a tool running locally in the browser can do.
compauth in Microsoft 365: Composite Authentication and All Reason Codes
Microsoft 365 supplements SPF, DKIM, and DMARC with its own evaluation: compauth. What Composite Authentication checks, what pass, softpass, fail, and none mean, and what causes each reason code, from 000 to 905.
AuthMechanism 10 and AuthAs Internal: How Exchange Classifies Message Submission in the Header
The X-MS-Exchange-Organization-AuthMechanism header documents how a submitting server authenticated. Value 10 indicates a Receive Connector with Externally Secured and classifies external emails as internal, with consequences for spam filters, mail flow rules, and spoofing protection.
F5 BIG-IP as an Outbound Proxy for Bulk Email Delivery: Persistence, SNAT, Timeouts, and DNS Resolution
A bulk delivery of 1,000 emails per minute runs through a BIG-IP as an outbound proxy to the provider relay. This article explains why sticky sessions provide no benefit here, how to properly resolve the provider hostname using an FQDN node, and which SNAT, timeout, and connection-limit settings actually determine throughput.
Internal or External? Interpreting Exchange Hybrid Mail Headers: AuthAs, MessageDirectionality, and X-originatororg
In Exchange hybrid environments, header classification determines whether an email is treated as internal. Which headers carry the classification, how tenant attribution works through certificates and connectors, and how to identify a misrouted message.
Performing a BIOS Update Safely: A Guide Using ASRock AM5 as an Example, Including BitLocker Preparation
The complete BIOS update process using an ASRock AM5 board as an example: determine the version, verify the download using a hash, properly suspend BitLocker, boot into UEFI (even if F2 does nothing), update with Instant Flash, and configure settings sensibly after the update.
VPN Split Tunneling for Microsoft Teams: Routing Media Traffic Around the Tunnel
Teams calls over a VPN suffer from latency, jitter, and the detour through the VPN gateway. This article explains which Microsoft networks and ports handle media traffic, why IP-based split tunneling is superior to app exclusions, and how to implement it in consumer VPNs, WireGuard, OpenVPN, and enterprise clients.
Determining a Mail Server’s Load Profile: Bursts, Peak Rates, and Recipient Structure from Message Tracking
How many emails per minute does your mail server really process, and how high are the peaks? How to use PowerShell and Exchange Message Tracking to determine the real load profile: rates per minute and hour, burst duration, recipient structure, message sizes, and common analysis mistakes.
