Warm up new IPs or domains gradually: If you're starting to send from a new email domain or dedicated IP address (for example, you've switched to a new email service or are separating your email flows), don't send the entire volume at once. ISPs are wary of new senders sending high volumes (it could be an IP-hopping spammer). Instead, warm up the IP/domain by sending smaller volumes at first and gradually increasing over days or weeks. This allows you to build a positive reputation incrementally. When warming up, send to your most engaged subscribers first: their opens and clicks will signal good engagement to ISPs. Many ESPs provide guidelines or automated warm-up programs to help you do this. Patience is key: a steady build will pay off in higher inbox placements as you scale, while a sudden surge may be throttled or filtered as spam.
Beware of volume spikes: Even if you have a solid sending history, be cautious with sudden large campaigns. For example, an e-commerce site that usually sends 2 emails per week might decide to send 5 different emails during Black Friday week. That spike, especially if it’s to a full list each time, could impact deliverability. That doesn’t mean you can’t send more during special periods, but be careful. Sometimes splitting up your sending over a few days or segmenting your audience can mitigate issues. Also, make sure that large sends are truly targeted and necessary; don’t send to your entire database if only one segment is relevant.
Keep an eye on your open rates, click-through rates, and unsubscribe/spam rates as you adjust your frequency. If you notice cell phone database that your open rates are decreasing and unsubscribes are increasing as you increase your sending, that’s a sign that you may be sending too many emails. On the other hand, if you’re sending emails very infrequently and seeing low engagement, your list may be cooling off—you may need to send a little more often, or at least show up when you do send. It’s a fine balance that you can fine-tune by looking at these metrics.
Send at optimal times, if possible: While not a critical deliverability factor, sending when subscribers are likely to check their email can maximize engagement (which indirectly benefits deliverability). Research on the best times to send can guide you (for example, some studies have found that mid-morning or mid-week often works well). Above all, avoid sending in the middle of the night or other odd hours if your audience is local—you don’t want your emails to always be buried under a pile of more recent morning emails when the user wakes up.