Scope the failure#
Record which domains, times and sending hosts are affected. A remote-system error does not, by itself, establish that the recipient address is wrong. Check whether the sending platform reports an incident or a delivery delay.
Use the surrounding evidence#
Review routing, DNS and connection logs. If an operator mentions reputation or policy explicitly, investigate that statement. Do not infer an IP reputation problem solely from a generic connection failure.
Keep an owner and a retry policy#
Let one system own delivery retries. Track unresolved attempts separately from permanent failures. If the issue repeats, send the service operator a concise incident packet and avoid scaling volume while the path is unstable.