If you find that your report is too large to send then the likelihood is that it can be resolved by reducing the quality of the images.
To do this, head to the Settings tab and reduce the 'Report Image Quality' slider. This determines the resolution of the images on the final report, so reducing it will also reduce the file size.
Generally, you should try to keep your reports under 20mb as most email clients and servers will not accept attachments that are larger than this.
The file size of a report will be listed after its generated in the bar at the top of the screen.