Hello @StanB840 ,
Bounces can end up varying depending on the receiving end's messaging. If we receive a block in one instance then an undeliverable coded message in the next, that's what our system will be reporting. You're welcome to reach out to our Delivery support for additional insight, or to go over a particular domain that seems to be regularly inconsistent. Otherwise, I'd recommend defaulting to getting rid of certain bounces types our system recommends, as outlined in this article.
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