Mail & SMTP

Total: 37

sendmail -t -i and -bs: What the Flags Do

Understand what sendmail -t, -i, and -bs do, how they differ across Sendmail, Postfix, and Exim, and how to test each mode safely.

Published: 11.09.2026

Message has a DKIM or DK signature, not necessarily valid: what it means and how to check DKIM

What DKIM_SIGNED means in SpamAssassin, when DKIM is actually broken, and how to check the signature, selector, DNS, keys, mail flow, and DMARC.

Published: 11.09.2026

Gmail 550-5.7.1 “Likely Unsolicited Mail”: Causes and Troubleshooting

A detailed guide to Gmail 550-5.7.1: checking bounce messages, SPF, DKIM, DMARC, PTR, IPv6, IP/domain reputation, and unwanted mail sources.

Published: 11.09.2026

Domain Has Exceeded the Max Defers and Failures per Hour

Fix the cPanel/Exim max defers and failures per hour error by tracing failed mail, finding the sender, stopping the source, and verifying recovery.

Published: 11.09.2026

SpamRL Blacklist: How to Diagnose and Fix Malicious URL Mail Blocks

Diagnose SpamRL mail rejections, isolate blocked URLs, inspect Exim or Postfix logs, verify domains, handle delisting, and prevent repeat blocks.

Published: 11.09.2026

What Is clientconfig.microsoftonline-p.net? Complete Setup Guide

`clientconfig.microsoftonline-p.net` is the autodiscover CNAME endpoint that Microsoft 365 / Outlook uses for client configuration discovery. Walk through when and why to add the CNAME (`autodiscover.yourdomain.com → autodiscover.outlook.com` is more common today), the verification flow, common errors, and the implications for hybrid on-prem Exchange + cloud setups.

Published: 06.06.2026

mx10.mailspamprotection.com: Understanding and Configuring It

mx10.mailspamprotection.com is one of SpamExperts' MX endpoints — when your MX records point at it, inbound mail goes through SpamExperts' filtering before reaching your mailbox server. Walk through the architecture, MX setup priorities (mx10/20/30/etc.), administration of the filtering rules, troubleshooting delivery delays, and the value proposition vs running your own filter.

Published: 24.05.2026

SMTP Hosting: Setup and Usage Guide

Choosing and configuring SMTP-hosting (a dedicated SMTP relay for outbound mail). Walk through the providers (transactional services like SendGrid/Mailgun/SES vs self-hosted Postfix/Exim), authentication setup, configuring common mail clients/CMS to use the relay, testing the connection, monitoring logs, and the security baseline.

Published: 18.02.2026

MailSpamProtection: Overview and How It Works

Comprehensive overview of mail spam protection: how content + reputation + authentication signals combine into a spam score, the major tools (rspamd, SpamAssassin, Imunify Email, Cloudmark), how to configure them for new installs, monitor effectiveness, and prevent both inbound spam from reaching users and outbound spam from your users reaching others.

Published: 04.07.2025

/usr/sbin/sendmail -t — Sending Email with File Attachment (Script Example)

Walk through a complete bash/PHP script that sends a message with a file attachment via sendmail -t. Covers the MIME multipart/mixed structure, base64-encoding the attachment, the headers required, common errors (missing Content-Type boundary, wrong line endings), and when to switch to a proper SMTP library instead.

Published: 23.03.2025

Setting Up DKIM with Exim

Exim signs outbound mail with DKIM via the `remote_smtp` transport — but only if `dkim_domain`, `dkim_selector`, and `dkim_private_key` are configured and the key file is readable by Exim. Walk through generating a 2048-bit keypair, publishing the DNS TXT record, wiring up the Exim transport, and verifying with a test message.

Published: 28.11.2025

"Domain of <sender> designates <IP> as permitted sender" — SPF Explained

"Domain of X designates Y as permitted sender" is the standard SPF-pass message embedded in email headers. Walk through what it means, how SPF works under the hood (TXT lookup, mechanism evaluation, result), the per-status-code meanings (pass, softfail, fail, neutral, none, temperror, permerror), and how to configure SPF correctly for common scenarios.

Published: 05.06.2026

Using /usr/sbin/sendmail -t to Send an Email from the Command Line

Hands-on examples of using sendmail -t from a shell session — single-line echo-pipe-sendmail pattern, multi-line heredoc, embedded headers with To/Cc/Subject, multiple recipients via headers, the typical scripting patterns, and the troubleshooting when CLI works but cron-driven invocation fails.

Published: 12.10.2025

How to Verify MX Records for mailspamprotection.com

When you've pointed your domain's MX records at SpamExperts (mailspamprotection.com) for inbound mail filtering, verify they're published correctly: `dig MX`, priority correctness (mx10/20/30 ascending or all-same), online tools that check propagation, and troubleshooting when MX shows in your DNS panel but mail still goes elsewhere.

Published: 03.03.2025

What is ESMTPA?

ESMTPA = ESMTP with Authentication. Walk through what each letter means (Extended SMTP + Auth), how it differs from plain SMTP (auth required = submission), the typical port (587 with STARTTLS), how to configure servers and clients for ESMTPA, and the security implications.

Published: 22.04.2026

How to Link a Domain with Yahoo Mail and Use It as a Corporate Email

Walk through using a custom domain with Yahoo Mail (Yahoo Small Business / Aabaco) for corporate email. Covers choosing the right Yahoo plan, the DNS records to publish (MX, SPF, DKIM, autodiscover), verifying ownership, creating mailboxes under your domain, and the access methods (webmail, IMAP/SMTP) plus testing.

Published: 16.05.2026

sendmail -t -i and -bs: What the Flags Do

Message has a DKIM or DK signature, not necessarily valid: what it means and how to check DKIM

Gmail 550-5.7.1 “Likely Unsolicited Mail”: Causes and Troubleshooting

Domain Has Exceeded the Max Defers and Failures per Hour

SpamRL Blacklist: How to Diagnose and Fix Malicious URL Mail Blocks

What Is clientconfig.microsoftonline-p.net? Complete Setup Guide

mx10.mailspamprotection.com: Understanding and Configuring It

SMTP Hosting: Setup and Usage Guide

MailSpamProtection: Overview and How It Works

/usr/sbin/sendmail -t — Sending Email with File Attachment (Script Example)

Setting Up DKIM with Exim

"Domain of <sender> designates <IP> as permitted sender" — SPF Explained

Using /usr/sbin/sendmail -t to Send an Email from the Command Line

How to Verify MX Records for mailspamprotection.com

What is ESMTPA?

How to Link a Domain with Yahoo Mail and Use It as a Corporate Email

Hosting

Cloud Solutions

For You

VDS

Website Builders

Our services

Client Area

sendmail -t -i and -bs: What the Flags Do

Message has a DKIM or DK signature, not necessarily valid: what it means and how to check DKIM

Gmail 550-5.7.1 “Likely Unsolicited Mail”: Causes and Troubleshooting

Domain Has Exceeded the Max Defers and Failures per Hour

SpamRL Blacklist: How to Diagnose and Fix Malicious URL Mail Blocks

What Is clientconfig.microsoftonline-p.net? Complete Setup Guide

mx10.mailspamprotection.com: Understanding and Configuring It

SMTP Hosting: Setup and Usage Guide

MailSpamProtection: Overview and How It Works

/usr/sbin/sendmail -t — Sending Email with File Attachment (Script Example)

Setting Up DKIM with Exim

"Domain of <sender> designates <IP> as permitted sender" — SPF Explained

Using /usr/sbin/sendmail -t to Send an Email from the Command Line

How to Verify MX Records for mailspamprotection.com

What is ESMTPA?

How to Link a Domain with Yahoo Mail and Use It as a Corporate Email

Hosting

Cloud Solutions

For You

VDS

Website Builders

Our services

Client Area

Выберите валюту