In spite of our best efforts to establish the same testing conditions for each tool, it’s true that other factors can play an important role. As the sender, you have a responsibility to do your best to increase deliverability by authenticating emails using SPF and DKIM and following best practice guidelines for creating and sending emails. Here are a few other pointers to bear in mind:

Content

Try to only send emails people actually want to receive, i.e. only send to fully opted in lists. Sending emails to non-permission based lists will result in low open rates, high unsubscribe rates, and high spam complaints, all of which indicate an unsuccessful email.

These kinds of results can have a negative effect on sender reputation and will impact future deliverability.

Frequency

Find the right balance between sending too many and too few emails to your subscribers. Remember that people are bombarded with tons of emails on a daily basis, so, in order to avoid inbox fatigue, only send what’s necessary.

You can even ask them to set the frequency at which they’d like to receive emails from you in their preferences. This can avoid spam complaints.

Monitoring activity

It’s not a good idea to have inactive people on your list as, if you’re sending emails to them regularly, this can affect sender reputation and impact deliverability.

Make sure to regularly check in with the less active people and give them the opportunity to re-engage or opt-out of future emails.