Since I wrote about it last month the requirements for bulk senders to Yahoo and Google have changed a little.
The big change is that bulk senders need to authenticate with both SPF and DKIM, rather than SPF or DKIM. Only one of those has to align with the 822 From: header.
If you’re an ESP with small customers you may have looked at the recent Google / Yahoo requirements around DMARC-style alignment for authentication and panicked a bit.
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451 Message temporarily deferred due to unresolvable RFC.5321 from domain; see https://postmaster.yahooinc.com/error-codes
A few months ago, Google made a splash in the political press and the email marketing space when they asked the FEC the following question:
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