Cold email glossary
Sender reputation
Sender reputation is the trust assessment mailbox providers assign to a sending domain and IP address based on its history of spam complaints, bounces, engagement, and authentication. It is the main input providers use to decide whether mail reaches the inbox.
What is sender reputation?
Sender reputation is not one number. Each mailbox provider, Gmail, Microsoft, Yahoo, and the rest, maintains its own internal assessment of every sender, built from the signals it observes: how often recipients mark mail as spam, how many addresses bounce, whether the sender hits spam traps, how volume behaves over time, whether SPF, DKIM, and DMARC pass, and how recipients engage with what arrives.
Reputation attaches to both the sending IP address and the sending domain. For most cold email senders the domain matters more, because mail goes out through Google Workspace or Microsoft 365, whose IPs are shared across a vast pool of senders and carry the provider's own reputation. DKIM ties each message to your domain, so your domain accumulates the track record and pays the price for mistakes.
Reputation moves with every send, and it moves asymmetrically: it degrades quickly and recovers slowly. A volume spike, a stale list with high bounces, or a burst of complaints can undo weeks of careful sending in a few days. Google and Yahoo's published bulk sender guidance makes some expectations explicit, including keeping spam complaint rates below 0.3 percent, authenticating with SPF, DKIM, and DMARC, and supporting one-click unsubscribe. Google Postmaster Tools is the main free window into how Gmail rates your domain.
Why it matters in cold email
Reputation is the gatekeeper for everything else in cold email. Targeting, copy, and offer only matter if the message is seen, and reputation decides that. Because reputation attaches to the domain itself, a hit taken while prospecting follows your invoices, support replies, and every other email the business sends from that domain. Running outbound on dedicated sending domains keeps the asset you can least afford to lose out of the line of fire.
How Sendful handles it
Sendful builds and protects reputation deliberately: dedicated domains registered and authenticated for each client, warmup before any outreach goes out, verified lists, conservative per-inbox volume, and continuous monitoring of bounces, complaints, and reputation signals so sending slows the moment they turn. All of that history accrues to dedicated domains, keeping your primary domain out of outreach entirely.
How do I check my sender reputation?
Google Postmaster Tools shows Gmail's view of your domain reputation and spam rate once you verify the domain. Beyond that, check the major blocklists, run seed placement tests, and watch your own bounce and reply trends. There is no single universal score; you assemble a picture from each provider's partial view.
How long does it take to repair a damaged sender reputation?
Typically weeks of consistent, low-volume, low-complaint sending, and longer if blocklists or spam traps were involved. Recovery means fixing the cause first, usually authentication, list quality, or pacing, then rebuilding slowly. In severe cases, moving outreach to a fresh dedicated sending domain can be more practical than waiting out a long rehabilitation.
What hurts sender reputation the most?
Spam complaints carry the most weight; Google and Yahoo's bulk sender guidance treats a complaint rate above 0.3 percent as a serious problem. High bounce rates from unverified lists, spam trap hits, sudden volume spikes, and failing authentication all compound the damage. Most reputation problems trace back to list quality and pacing rather than copy.
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