Could you possibly help me to fix an issue with email deliverability?

When we sent out the digi docs campaign it was meant to be sent to 562 people which it was – however the delivery rate was significantly low. I have attached an image of the stats below so you are able to see.

Is there any way that we are able to ensure that the delivery rate is significantly higher? You can see below that the rate of sent and rate of delivery is not in proportion and for the next email we sent out we would like a higher rate.

If you could get back to me that will be great.

Regards,

Aliza Visram