Hi @JLaugharne7,
Thank you for reaching out to the Community!
Just to clarify, you are sending the emails from Gmail (you have installed the extension HubSpot Sales for Gmail). You are not sending from HubSpot. Please let me know if that’s not the case.
I’d like to share these resources that might help you:
- Surviving Your First Email Campaign in HubSpot [Customer Story]
- The solution from @karstenkoehler on this post “Drop in email open rate”
- The solution from @danmoyle on this post “Open rate drops”
- The solution from @karstenkoehler on this post “Lower open rates in HubSpot compared to other platforms”
I also wanted to invite a couple of subject matter experts to this conversation: Hi @danmoyle, @beeginman and @Jnix284 do you have tips and advice to share with @JLaugharne7, please?
If anybody else has anything to add and/or share, please feel free to join in the conversation 
Thank you and have a fantastic day!
Best,
Bérangère