Interspire Email Marketer taking long time to send bulk emails

I am using Mailjet SMTP Server along with Interspire Email Marketer to send emails to a large group of users (around 54,000). I once used Mailjet's inbuilt Email Marketer to perform a similar function, and it took only about 45 minutes to send all the emails. However, Interspire Email Marketer takes about 18-20 hours to send the same number of emails.

We know that Interspire Email Marketer has to interact with the external Mailjet SMTP, but is there anyway we can reduce the time taken by Interspire to send the emails? Any help would be appreciated.

Solution 1:

This answer is generic, rather than specific to Mailjet. I am not familiar with that particular software, but I am all to familiar with being on the receiving side of automated deliveries.

The first thing I would to is ensure your rDNS validates and your mail server identifies itself with that domain name. Also make sure your mail server accepts messages to postmaster, abuse, and the envelope address you are using.

I would expect you are paying the cost of a higher delivery rate. Given the time taken without the SMTP server, I would expect you had a number of failed deliveries to servers which avoid accepting SPAM. Some of the problems you would encounter sending my server mail:

• Delays connecting while DNS is verified.
• More delays if DNS is not fully correct.
• Delays running SPF checks.
• Delays verifying HELO name.
• Callout to verify you have an MX.
• Greylisting refusing initial delivery.

An SMTP server will take longer to deliver in these cases, but it is more likely to deliver. If your configuration is not correctly done, you still will have failed deliveries.

If you aren't delivering personalized messages, then sending to multiple recipients in one request may help. Depending on how the SMTP server works, sending to multiple recipients in the same domain may be better.

In general these settings, if available, should help.

• queue only delivery. Messages are queued for delivery, rather than delivered immediately.
• multiple deliveries per connection. Multiple messages for the same domain are delivered in on connection. (Requires queuing.)
• multiple queue runners. More than one process will be delivering email.
• multiple queues. Reduces access contention on the queues.
• separate retry queue/server. Reduces the requirement to skip messages in the queue(s) which haven't reached their retry time.