A number of people have mentioned over the last couple weeks that they’re seeing a spike in Yahoo rejecting mail with
554 delivery error: dd Requested mail action aborted
Discussions on various mailing lists indicate these messages are related to inactive accounts. Addresses that bounce at Yahoo with these codes should be handled as inactive addresses and removed from future mailings.
Spike in Yahoo error codes
S
RSS - Posts
For us, the issue started on October 23, 2017 and applies to Sendgrid but not to Amazon SES.
Update: It turns out we don’t record the bounce reason for SES, so it may or may not be affected.