As reported here and elsewhere, Yahoo has reduced the amount of free storage for Yahoo Mail users. The prior limit, 1 terabyte, is now reduced to 20 gigabytes. Users with a mailbox containing with more than 20 gigabytes of messages will be unable to send or receive email until they clear space or purchase additional space. This updated limit took effect on August 27, 2025.| Spam Resource: All Things Deliverability
Here's one I hadn't seen before. A sender was hitting this deferral when trying to deliver mail to Microsoft (Hotmail/Outlook.com) domains: ...| www.spamresource.com
Seen this recently? 451 Message temporarily deferred due to unresolvable RFC.5321 from domain; see This is Yahoo doing some extra work to identify that the 5321.From domainThe return-path, aka the …| Word to the Wise