The last few sends have seen a significant increase in blocked bounces, which makes me think we're dealing with a sender reputation issue. We're using a SAP with a shared IP and only sending to about 1,000 recipients per month. Are there any common reputation-related issues I should be looking into beyond authentication and content testing? I've tested the emails in Email on Acid and they're returning low spam scores, so I'm struggling to identify the root cause.
I'm also considering switching to a sending domain used by another BU that has significantly higher volume. However, I'm concerned that if the underlying reputation issue isn't addressed, the problem will just follow us. Has anyone tried this approach, and did it actually help?
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A few things stand out. At ~1,000 sends/month, a shared IP is actually the right call — a dedicated IP needs steady high volume (think 100k+/month) to stay warm, so moving to one would likely hurt deliverability, not help. The trade-off of a shared IP is that your reputation is partly tied to the other senders in that pool, so a sudden jump in blocked bounces can come from them even when your own auth and content are clean (which your Email on Acid scores back up).
Because your volume is low, reputation is domain-driven more than IP-driven — so check Google Postmaster Tools (domain reputation + spam rate) and pull your bounce logs to see exactly which receiving domains are blocking and the reason they give; a blocked bounce almost always names a blocklist or policy. Worth checking the shared IP against Spamhaus too.
On switching to the other BU's domain — I'd hold off. That mostly moves the problem (and risks dragging their domain down); better to pin down the actual block source first.
If this helps, please mark it as the Best Answer so it helps the next person — thanks 🙂
