Sender Reputation

Sender reputation is one of the most important and least visible variables in email deliverability. Every mail provider maintains an internal score for each sending domain and IP, and that score determines whether your emails land in the inbox or the spam folder.

How reputation is calculated

Mail providers use proprietary scoring systems but the inputs are well-understood:

Bounce rate. Hard bounces (recipient address does not exist) signal that the sender is using scraped, outdated, or fake lists. A bounce rate above 2-3 percent damages reputation quickly. Above 5 percent and emails start landing in spam reliably.

Spam-complaint rate. When recipients mark email as spam, the receiving provider records it and applies it to the sender's reputation. Even small spikes (above 0.1 percent of sends) damage reputation. The spam-complaint signal is the most-weighted input because it reflects active negative judgment from real recipients.

Recipient engagement. Opens, clicks, replies, forwards, and "moved to important" actions are positive signals. Deletes without reading, especially deletes-without-opening, are weak negative signals. The engagement window matters too — engagement within hours signals more than engagement after days.

Consistency. Sudden volume spikes (e.g., from 100 emails per day to 5,000) trigger spam-pattern detection. Senders with consistent volume over time accrue better reputation than senders with erratic patterns.

Authentication. SPF, DKIM, and DMARC alignment is increasingly weighted as a positive signal. Missing authentication damages reputation; complete authentication contributes to it.

Domain reputation vs IP reputation

Two distinct scores. Domain reputation follows the sending domain (yourdomain.com) wherever it sends from. IP reputation follows the specific sending IP — Google Workspace shares IPs across many senders, while a dedicated IP (typical for high-volume transactional or marketing senders) has its own dedicated reputation.

For B2B sales teams sending from established business inboxes (Google Workspace, Microsoft 365), both reputations are managed by the email provider. The team's actions affect domain reputation but not IP reputation directly.

For teams sending through cold-outreach platforms (Saleshandy, Snov.io, Lemlist) or transactional email services (Mailgun, SendGrid, Postmark), IP reputation becomes more visible because dedicated IPs are common. A new dedicated IP starts with neutral reputation and needs to be warmed up.

What damages sender reputation

Five common causes, ranked by impact:

Hitting spam traps. Spam traps are email addresses set up by anti-spam organisations specifically to catch spammers. Sending to one — usually because the sender bought or scraped a list that included it — immediately damages reputation.

High bounce rate from list quality issues. Sending to invalid addresses, old addresses, or addresses that have moved triggers hard bounces. The bounce rate signal damages reputation proportionally.

Spam complaints from recipients. Active negative judgment. The most damaging single signal because it reflects real-recipient unwantedness.

Sudden volume spike. A jump from low-volume to high-volume sending without warm-up is the canonical spam pattern. Modern providers detect it and throttle deliverability immediately.

Authentication failures. Sending without proper SPF/DKIM/DMARC, or with broken authentication, damages reputation over time. The damage is slower than the others but compounds.

How to monitor sender reputation

Three free tools cover most B2B teams' needs:

Google Postmaster Tools. Free dashboard from Google showing sender reputation (Bad, Low, Medium, High) for your domain, authentication rates, spam rate, IP reputation, and feedback loop data. The single most useful tool for monitoring B2B sender reputation if you send to Gmail recipients.

Microsoft SNDS (Smart Network Data Services). Free dashboard from Microsoft showing IP reputation, spam complaints, and recipient feedback for sends to Microsoft 365 and Outlook.com recipients.

Sender Score (Validity). Third-party reputation score (0-100) maintained by Validity. Free to check at senderscore.org. Useful for benchmarking but Google Postmaster Tools and Microsoft SNDS are more authoritative for the actual mail-provider behaviour.

How to recover damaged sender reputation

Slowly and deliberately. Three steps that work:

Fix the underlying problem first. If the damage came from high bounces, clean the list and stop sending to bounced addresses. If from spam complaints, change the messaging or the audience. Sending more from a damaged reputation makes it worse.

Reduce volume dramatically. Cut sending volume by 80-90 percent for a few weeks. Send only to highly engaged recipients (those who have replied or opened recently). Build positive engagement signals slowly.

Re-warm the sending domain. Use a warm-up service to send conversational test emails between your sending domain and a network of warmed accounts that mark them as not-spam and reply. This is the same warm-up technique used for new domains.

Reputation recovery typically takes 4-12 weeks of clean sending. There is no shortcut.

What Outsolvi does (and doesn't do) for sender reputation

Outsolvi does not send emails for you. You send from your own Outlook or Gmail account, so your sender reputation is whatever your established business inbox already is — typically already good. Outsolvi tracks the sends but does not affect the sending path or contribute to reputation damage from inflated volume.

For teams using Outsolvi alongside a cold-outreach platform (Saleshandy, GMass), the cold-outreach platform handles its own sender reputation (typically through warm-up tooling and sender rotation) while Outsolvi handles the tracking layer on the established-inbox sends.