I've had a customer start getting lots of non-delivery replies from
Outlook.com with code "550 5.7.515"
This page suggests that it's a requirement for "high volume senders" to use
DKIM as well as SPF and DMARC:
https://support.microsoft.com/en-us/outlook/fix-ndr-error-550-5-7-515-in-outlook-com
Sadly is doesn't say over what time period "5,000 messages" is measured
over, for a sender to be classed as "high volume". Nor does it say when
this requirement for DKIM came into effect.
Does anyone know?
Is this a relatively new requirement from Outlook.com?
Anthony
--
www.fonant.com - Quality web sites
Tel. 01903 867 810
Fonant Ltd is registered in England and Wales, company No. 7006596
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