I think you would need to optimise the email content itself to get any observable difference on server load. It would highly depend on what are you sending in the email blast.

If the the email content is not personalised based on the customer I would recommend generating a static html of the the content (even if the content itself is dynamically generated, if the email content doesn't vary based on customer you should use a single static html once it's generated). This way the only load on the server will be of sending the static html as email instead of every email querying DB for the same thing over and over.

Also, regarding the access.logs you should closely look into the urls and check if the urls are the media and content used in the emails themselves. If it's that it's actually a good thing as customers are opening your emails and that maybe generating those logs.

I think you would need to optimise the email content itself to get any observable difference on server load. It would highly depend on what are you sending in the email blast.

If the the email content is not personalised based on the customer I would recommend generating a static html of the the content (even if the content itself is dynamically generated, if the email content doesn't vary based on customer you should use a single static html once it's generated). This way the only load on the server will be of sending the static html as email instead of every email querying DB for the same thing over and over.

Also regarding the access.log, you should closely look into the urls and check if the urls are the media and content used in the emails themselves. If it's that, it's actually a good thing as customers are opening your emails and that maybe generating those logs.