Thank you for reaching out about this! Luke from the Front Support Team here  

In regards to the 100 attachments error message, this is caused by how past messages (and their attachments) are reflected when replying to an email. 

When you reply, all previous messages are folded under the one you are currently composing. As a result, any images or files in the previous messages are included, such as the images included signatures.

What has happened is that the thread you were replying to already contained 100 attachments. So when you clicked to reply to the message, those attachments were also being counted in your message. 

To get rid of those duplicate attachments, and the error message, you can clear the previous attachments like so:

1. Look at the bottom of your message, below your signature, there are three dots, click them.
2. This will show the previous messages, click the X on the right side to delete all past data/images. The X will appear while hovering your mouse over the section you'd like to delete, you may need to move the mouse to see it appear.

I hope this helps but please do not hesitate to reach back out should you need any additional assistance or have any other questions. I'm more than happy to assist! 

All the best, 

Luke