Best sending practices for B2B outreach

Warmup, daily limits, attachments, copy quality, and inbox placement operations.

Warm up gradually

Start with low daily volume per mailbox and increase only after stable delivery and positive engagement signals. New or idle inboxes should not jump to full campaign volume on day one.

Respect daily and hourly limits

Distribute sends across a mailbox pool and avoid bursty behavior. Consistent moderate sending outperforms spikes that trigger rate limits at Google, Microsoft, or your SMTP provider.

Attachment usage

Use attachments only when needed. Keep files small, avoid executable types, and do not repeat large sends at scale, because attachments increase spam-score weight.

Spam-trigger avoidance

Keep language natural and specific to the recipient. Limit all-caps, urgency-heavy wording, excessive links, and image-only emails.

Weekly monitoring routine

• Track bounce rate by mailbox and provider.
• Track reply quality, not only quantity.
• Reduce volume immediately on negative trend shifts.
• Tune copy and targeting before increasing send limits.
• Review spam complaints and unsubscribe intent replies.