In this blog, we shall discuss how to keep SMTP connection persistent and alive for Batch Sending and how to use currently available SMTPs in a Loop, during the warm-up session.

Most of you might already have updated your Mumara to the latest version, but if you still haven’t updated it, do it today. A few previous updates have added a little extra, in terms of convenience, usability, and user experience.

Towards the 3rd step of “Scheduling Email Campaign,” you will notice a couple of choices for the SMTP Sequence. This new addition will enhance your control to choose between the “Batch” and “Loop” sequences of selected SMTP accounts.


Do you want to send fast and bulk? The batch sequence of SMTP will help you to keep the SMTP connection alive. Persistent SMTP connection eventually results in preventing unwanted delays in sending. Selection of this option will automatically set the batch sequence.

SMTP sequence - Batches | Mumara

Dividing the number of emails in the campaign to send by a number of selected SMTPs. The maximum batch size is 500 emails per SMTP. It means you can keep the SMTP connection persistent for the batch of 500 email sends. Let’s take an example of a custom-configured mail server to understand more about the “Batch” sequence of SMTP.

The example server has 5 IPs, each SMTP is configured with one separate IP and you eventually have 5 SMTP accounts within Mumara. The campaign you are scheduling is set to reach 1,500 subscribers, you have selected 3 SMTP accounts from the available 5, and “Batches” is the selected sequence of SMTP.

It will establish the connection to the first SMTP that will remain alive until it finishes its batch of 500 emails. Once the first SMTP connection is closed, the persistent connection with the second SMTP is established to send its batch of 500. It is how it works for the maximum batch size. The end result of this type of SMTP sequence will help reduce sending time to a large extent.


Are you sending IPs a warm-up campaign? Batches may not be the fitting choice of the SMTP sequence when the IPs are new and you are trying to increase sending reputation.

sending emails in loops | Mumara

In this case, you may need more frequently rotating SMTP connections. “Loop” is the suitable choice of SMTP sequence. Let’s take the aforementioned example of a custom server, when the “Loop” sequence is checked as the preferred choice, among the 5 SMTP accounts, 3 are selected to send 1,500 emails.

It will take the first SMTP and will close the connection after sending the first email, the next SMTP will send the second email and the third will send the third. This cycle repeats from 4th email, and the loop behavior continues, until it finishes 1500 emails. Even in this case, each IP will send 500 emails, but the SMTP connection will not remain persistent.

This SMTP sequence suits best when you want to limit your sending speed and time, in the midst of the most crucial phase of IP warming or improving sender scores.

This option gives enhanced control to automatically switch among SMTP connections by setting up sending limits. So this addition of SMTP sequence can really help to customize sending pattern according to your need.

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Eric Lee

A reader, writer, researcher, and explorer!

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