iCloud Mail postmaster information: mail acceptance rules, expected authentication, rejection codes and the contact procedure for blocked senders.
Ecosystem directory
Organizations, events and solutions of the email ecosystem. Every entry is verified and dated.
Operators' postmaster pages
Operators' postmaster pages: sending rules, error codes, unblock and contact forms.
Comcast (comcast.net) postmaster page: sending rules, error codes, unblock requests and feedback loop registration.
Free postmaster page (free.fr): sending rules, rate limits, SMTP error codes and contact procedure for senders.
GMX postmaster page (1&1 Mail & Media): sending requirements, error codes, unblock procedure and registration for the operator's whitelist and feedback loop.
Google's reference page for senders to Gmail: authentication requirements (SPF, DKIM, DMARC), one-click unsubscribe, complaint thresholds, and a pointer to Postmaster Tools for reputation monitoring.
laposte.net postmaster page: mail acceptance rules, expected authentication, rejection codes and sender contact.
Mail.ru's postmaster tracker, called @Postmaster: deliverability statistics per sending domain (reads, deletions, complaints, placement), sending rules and feedback loop for mail.ru, bk.ru, inbox.ru and list.ru mailboxes.
Postmaster page for Outlook.com, Hotmail and Live: sending policies, SMTP error codes, unblock request form, and access to the SNDS (per-IP data) and JMRP (feedback loop) programmes.
Orange postmaster page (orange.fr, wanadoo.fr): sending rules towards its subscribers, error codes, contact form for senders and information on complaint handling.
T-Online (Deutsche Telekom) postmaster page: sending rules, technical requirements (reverse DNS, authentication), error codes and sender contact.
WEB.DE postmaster page (1&1 Mail & Media): same rules and procedures as GMX, for web.de mailboxes.
Postmaster page shared by Yahoo Mail and AOL: sending best practices, authentication and unsubscribe requirements, error codes, and request forms for assistance and the feedback loop.
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