Avoid purchased email lists
Addresses obtained from a third party rarely carry the clear, current relationship needed for responsible email. They commonly produce complaints, bounces and lasting reputation damage. Read more
Email Deliverability Guide
Actionable guidance to help legitimate email pass authentication checks, protect sender reputation and reach the inbox.
Deliverability is affected by much more than the SMTP connection itself. Use these guides to review the identity, structure and operational practices surrounding the messages you send through AuthSMTP.
List Management
Build permission-based recipient lists, preserve consent records and suppress addresses that no longer belong in active mailings.
Confirmed opt-in
A confirmation step proves that the address works and that its owner controls it. It prevents many typing errors, forged subscriptions and immediate complaints. Read more
Email list quality
A list becomes less reliable as addresses, roles and recipient expectations change. Keeping inactive contacts indefinitely increases bounces and complaints without adding useful reach. Read more
Authentication
Authorise legitimate senders and align your domain with SPF, DKIM and DMARC.
Use your own domain
Free mailbox domains control their own authentication policies and may not authorise third-party SMTP services. Your own domain provides a stable identity you can configure and protect. Read more
Reverse DNS, PTR and HELO
Receiving systems expect the delivering server to present a stable hostname with coherent forward and reverse DNS. Missing or generic identity weakens trust. Read more
TLS for email transport
TLS protects SMTP traffic while it crosses a network, but it is transport encryption—not end-to-end encryption of the message stored in a mailbox. Read more
SPF and AuthSMTP
SPF tells receiving systems which services may send mail for a domain. Your record must cover AuthSMTP and every other legitimate source without creating a second SPF record. Read more
DKIM signing
DKIM adds a cryptographic signature that lets recipients verify the signing domain and detect changes to signed message content. Read more
DMARC
DMARC connects SPF and DKIM results to the domain recipients see in the From field, then publishes handling and reporting policy for failures. Read more
Dedicated IP addresses
A dedicated IP isolates reputation but also removes the protection of a well-managed shared pool. Low or irregular volume may not establish a useful reputation. Read more
Sending Strategy
Use stable identities, balanced traffic and separate mail streams to protect important messages and sender reputation.
One message per recipient
Putting a mailing list into To, Cc or Bcc creates privacy, tracking and complaint-handling problems. Individually addressed messages are safer and easier to manage. Read more
Avoid no-reply addresses
A no-reply identity frustrates recipients and removes a useful route for questions, corrections and positive engagement. A monitored response address builds more trust. Read more
Use a managed SMTP service
Reliable outbound email requires DNS, reputation, queues, security, abuse controls and monitoring. A managed service concentrates those operational responsibilities. Read more
Consistent sending volume
Large unexplained changes in volume resemble compromised or abusive traffic. Stable patterns make it easier for providers and your own team to recognise normal sending. Read more
Balanced provider delivery
Sending every Gmail, Microsoft or Yahoo recipient consecutively can create a provider-specific spike even when total campaign volume looks reasonable. Read more
Consistent sender identity
Frequent sender-name or address changes reset recognition and resemble impersonation. Stability strengthens trust and makes filtering decisions more predictable. Read more
Inbox placement expectations
The receiving provider and recipient ultimately control classification. Their private models, local rules and user choices can change without notice. Read more
Separate email streams
Promotional and transactional mail have different expectations and risks. Combining them lets complaints or poor engagement from one stream affect the other. Read more
Monitoring
Use delivery failures and provider feedback to find problems before reputation suffers.
Bounce handling
Delivery failures are operational feedback. Classifying and acting on them promptly protects list quality, sending reputation and future inbox placement. Read more
Spam complaint handling
A complaint is a strong signal that a recipient did not expect or want the message. Repeated sending to that address compounds the damage. Read more
Mailbox-provider feedback
Provider feedback can reveal authentication, complaint and reputation trends that are not visible from successful SMTP submission alone. Read more
Inbox placement monitoring
Internal logs show submission and delivery events, but test mailboxes reveal filtering, rendering and workflow problems from the recipient's perspective. Read more
Content & Formatting
Construct standards-compliant messages that render and travel reliably.
Recipient engagement
Messages that recipients repeatedly ignore, delete or report as spam teach mailbox providers that the mail is unwanted, even when authentication passes. Read more
Email content quality
Content should communicate its purpose without misleading urgency, image-only design or inaccessible presentation. Trust and usefulness matter more than avoiding a list of supposed spam words. Read more
Personalisation and segmentation
Useful personalisation reflects a genuine relationship or preference. Incorrect names, inferred sensitive details and excessive data use reduce trust instead. Read more
Sender contact information
Recipients should be able to identify the organisation, understand why it contacted them and find a dependable route for questions or rights requests. Read more
Email unsubscribe
When leaving is difficult, recipients use the spam button. A simple opt-out protects recipient choice and sender reputation. Read more
Email formatting and MIME
A message can look correct in a template preview and still be malformed as Internet email. Headers, line endings, MIME structure and transfer encoding all affect acceptance and filtering. Read more