Getting your emails delivered is the foundation everything else in email marketing depends on. No amount of great content or design matters if your emails never reach the inbox.

The core of deliverability: sender reputation

Mailbox providers like Gmail, Yahoo, and Outlook assign a reputation score to your sending domain and IP address, based on your sending practices, subject lines, content, and list quality. A poor reputation leads to emails landing in spam or being blocked entirely, regardless of how good the campaign itself is.

Authentication protocols

SPF, DKIM, and DMARC together confirm to receiving servers that you're a legitimate sender, protect your domain from being spoofed for phishing, and are now effectively mandatory given Google and Yahoo's current bulk sender requirements.

Warming up a new or low-reputation domain

A newly purchased domain, or one that's been used rarely, starts with a low, "cold" reputation among mailbox providers. Zoho recommends sending to around 5 to 10 percent of your recipients per day at first, rather than blasting hundreds of emails immediately, gradually increasing volume as engagement stays healthy. Domain warmup isn't a one-off task; it's an ongoing practice of watching open rates, click rates, spam complaints, bounces, and unsubscribes.

List hygiene

• Use verified, permission-based lists rather than purchased ones, to minimise bounces and spam trap hits
• Avoid emailing contacts with more than a year's gap in communication without a specific re-engagement (win-back) campaign first
• Encourage recipients to whitelist your address or add you to their contacts, which improves inbox placement over time

High-volume senders

Zoho Campaigns offers dedicated IP options for high-volume senders, so your reputation isn't affected by other customers sharing the same sending infrastructure.