New SMTP replies at Outlook: update your backoff patterns to avoid reputation damage

On April 5th, at 5AM CET, we were alerted by a huge spike in Outlook deferrals. The chart below (copied from Postmastery Delivery Analytics) reveals the deferrals over time: After investigating the issue, Postmastery delivery engineers discovered new SMTP replies at Microsoft domains. These errors are receiver’s side, not related to sender’s reputation. Organization queue quota […]

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Categories: Authentication, Deliverability, General, Providers

AOL and Yahoo merge could impact your email delivery and MTA

A few weeks ago, AOL reported that AOL and Yahoo will come together under the OATH umbrella and merge with the Yahoo email infrastructure to serve both brands. This happened on 20 February 2018, and now all the AOL recipient domains’ MX, including the following, will point to mx-aol.mail.gm0.yahoodns.net: – aol.com – verizon.net – aol.co.uk […]

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Categories: Authentication, Deliverability, General, PowerMTA, Providers

Case study – Why typo domains can cause severe email delivery issues

In our daily email delivery monitoring activities, we recently saw the damage that typo domains can do. In this case study, simple typos in domains caused severe email delivery issues. We will recap what happened and how we solved the issue. Hopefully, other senders can avoid this kind of situation in the future. Postmastery, we […]

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Categories: Authentication, Case Studies, Deliverability, General, PowerMTA