Guia do email

Reading a SenderRadar report block by block

Every block and badge of a SenderRadar report explained: whois, MX, SPF, DMARC, subdomains, wildcard, and what to do with each value.

SenderRadar FAQ: subdomains, wildcard, quotas, retention

Answers to frequent questions about SenderRadar: missing subdomains, wildcard, results kept 30 days, quotas, free service, feature requests.

Understanding SenderRadar: the email map of a domain

What SenderRadar shows about a domain (MX, SPF, DMARC, subdomains, wildcard), who the site is for and what it is not.

APR: aggregate reports on delivery performance

APR (Aggregate Performance Reporting) is an individual IETF draft proposing that mailbox providers send senders aggregate delivery reports. Status and idea.

ARC: preserving authentication results across relays

ARC chains cryptographic seals at every relay to preserve the original SPF, DKIM and DMARC results through forwarding and mailing lists. Who deploys it and how.

BIMI: showing a brand logo next to its messages

BIMI lets mailbox providers display the logo of an authenticated domain. DMARC prerequisites, SVG format, VMC and CMC certificates, DNS record and pitfalls.

DKIM2: the DKIM overhaul under way at the IETF

DKIM2 is an IETF project to replace DKIM: per-relay chained signatures, envelope binding, reversible modifications, an end to replay. Where the drafts stand.

DKIM: signing messages to prove origin and integrity

DKIM adds a cryptographic signature to messages, verified through a public key in DNS. Selectors, signed headers, key rotation and the mistakes to avoid.

DMARC: setting a policy and receiving reports for your domain

DMARC ties SPF and DKIM to the visible From domain, tells mailbox providers what to do on failure and sends back aggregate reports. Syntax, rollout, 2024 rules.

MTA-STS and TLS-RPT: requiring TLS on inbound mail and knowing when it fails

MTA-STS publishes a policy requiring verified TLS to a domain's MX hosts; TLS-RPT returns reports about failed connections. Records, policy file and pitfalls.

SPF: declaring who may send mail for a domain

SPF publishes in DNS the list of servers allowed to send mail for a domain. How it works, record syntax, the ten-lookup limit, deployment and common mistakes.

Subdomains and wildcards: what secondary names inherit (and what they do not)

SPF is not inherited, DMARC propagates to subdomains, DKIM depends on d=, and a DNS wildcard answers for every non-existent name. Rules and good practice.

Blacklists and DNSBLs: how blocklists work

How a DNSBL works, a sample query and reply, the well-known lists (Spamhaus, SpamCop, Barracuda, SURBL, URIBL), how to check a listing and how to get removed.

ESP: what an email service provider is and what it takes care of

What an email service provider does, shared versus dedicated IPs, the DNS records a customer delegates, how to spot the provider behind a domain, what to check.

Feedback loops and ARF: receiving complaints from recipients

What a feedback loop (FBL) is, the ARF format defined by RFC 5965 with a sample report, how to enrol with mailbox providers and what to do with every complaint.

MTA: the server that carries mail from one domain to another

What a Mail Transfer Agent does in SMTP delivery, how it differs from MUA and MDA, common software, which log lines to watch and the mistakes to avoid.

MX and reverse DNS: the records that make a mail server exist

How MX records, PTR records and FCrDNS work, with dig examples, what mailbox providers check on every connection and the mistakes that break delivery.

Postmaster tools: what Google, Microsoft and Yahoo show to senders

Google Postmaster Tools, Microsoft SNDS and the Yahoo Sender Hub: enrolment, the metrics each one exposes, how to read the dashboards and their limits.

Reputation and warm-up: earning the trust of mailbox providers

How mailbox providers score the reputation of an IP and a domain, which signals matter, a realistic warm-up schedule and the mistakes that undo it.