What are the impacts of fluctuating sending volume?

When you send steady and predictable email volume, mailbox providers can have more confidence in you. If your volume patterns fluctuate and you sometimes have sudden, dramatic volume increases, you show behaviors mailbox providers often see from spammers.

So if you don’t even out your volumes, you will usually see some negative effects in a few areas.


Mailbox providers decide how they want to treat your email based on your IP’s past behavior. They will probably throttle your email or deliver it to the bulk folder if your volumes fluctuate frequently. In general, your deliverability can be as unpredictable as your volume patterns.  

Mailbox providers are suspicious of senders with inconsistent sending volumes. A common technique spammers use, called batch and blast, involves emailing a large number of subscribers all at one time. They also don't usually have a regular mailing schedule the way a commercial sender should. Anytime your volume has a sudden and drastic increase, you can look like a spammer, and mailbox providers will often treat your email as such.

Simply, volume consistency is a best practice; without it, your deliverability performance will most likely suffer.

Sender reputation

Volume also plays a role in reputation. Spammers tend to send email to a huge number of addresses at once. Because of that, you’ll be under a high level of scrutiny if you send high volumes. Consistent volume and following best practices helps to alleviate this attention and establish a good reputation.

Common Issues

Volume inconsistency isn’t always the direct cause of deliverability problems. However, managing volume patterns will bring the best results in the following areas.

New IPs

Typically when sending from new IPs, you will often have some throttling since a reputation has not yet been established. The best way to start building a positive reputation is by warming up your IPs, which is a process of initially sending smaller volumes and gradually increasing them to develop a good reputation. Sending to only your most engaged subscribers at first is also a best practice.  


Complaint rates also go up and down when sending volumes fluctuate, and this has a reputation impact. Complaint rates are measured by the number of complaints divided by the total volume on a given day, so volume fluctuations can create spikes that do not necessarily represent true complaint rates.

Mailbox providers use the number of messages delivered to their customers' inboxes to determine the complaint rate for an IP. When high volume of email from an IP is delivered to the inbox, it takes a larger number of complaints to raise your complaint rate. Because subscribers do not always complain on the day an email was sent, complaints can come in for a campaign days or even weeks after the initial send. If the volume from an IP has decreased in that time, that can potentially inflate your complaint rate. If the volume had been consistent, your complaint rate would have been steady also.

The combination of inconsistent volume and what seems to be significantly elevated complaints can cause delivery issues and affect reputation.


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