Deliverability is whether your email reaches the inbox instead of spam folders or being rejected outright. No platform can guarantee inbox placement — mailbox providers decide based on signals they observe over time. The good news is that most teams can improve outcomes by focusing on a small set of practices that providers consistently reward.
What mailbox providers actually evaluate
Providers look at a mix of technical setup, sending behavior, and recipient engagement. Common factors include:
- Authentication — SPF, DKIM, and DMARC help providers verify that mail from your domain is authorized and has not been tampered with.
- List quality — Hard bounces, spam complaints, and low engagement tell providers your mail may be unwanted.
- Sending patterns — Sudden volume spikes from a new or idle mailbox can look risky compared with a gradual, consistent pattern.
- Content and relevance — Misleading subject lines, heavy image-only layouts, and poor list targeting can increase complaint rates.
SendWise treats these as ongoing disciplines. See our deliverability features for how warmup, verification, and per-sender caps fit into a healthy workflow.
Authentication: the baseline every sender should fix first
Before scaling volume, confirm that mail sent from your domain passes SPF and DKIM checks and that DMARC is published with a policy your team understands. Authentication does not guarantee inbox placement, but missing or misconfigured records are a common reason mail fails or lands in spam.
Work with whoever manages your DNS (often IT or your domain registrar) to align records with the mailbox or SMTP service you send from. If you connect Gmail or Microsoft 365 through SendWise, follow the provider-specific guidance in our integrations overview.
List hygiene beats volume tricks
A smaller, engaged list usually outperforms a large, stale one. Remove or suppress addresses that hard-bounce, mark you as spam, or have not engaged in a long time. Run list verification before major sends to catch invalid addresses early.
Permission matters. Send only to people who opted in to hear from you, and make unsubscribes easy. High complaint rates are one of the fastest ways to damage reputation across a domain.
Warm up new or idle senders
When you start sending from a mailbox that has little recent history — or after a long pause — increase volume gradually. Our email warmup guide explains how ramp schedules work and why they matter when you connect Gmail, Microsoft, or SMTP senders.
SendWise includes warmup on every plan so teams can build a healthier pattern without manual spreadsheet tracking.
Respect provider and platform limits
Gmail and Microsoft 365 apply their own sending limits that vary by account type and may change over time. Plan campaigns with those constraints in mind. Our guide on Gmail and Microsoft 365 sending limits covers what to check before you schedule large sends.
SendWise also applies per-sender daily caps as an additional safeguard — they encourage steady pacing rather than one-day blasts that can trigger throttling.
Monitor and adjust
Watch bounce rates, complaint signals, and engagement trends after each campaign. If metrics slip, reduce volume, tighten segments, and review list sources before pushing harder. Deliverability is iterative: small corrections early prevent larger problems later.
Before the next launch, use the SendWise email campaign checklist to review list quality, sender setup, content, delivery controls, and reporting. For product-level tooling, explore SendWise features or return to the Resources hub for related references.