Why some times I can not email my files?

Please check the size limit of your email provider for attachment. Most email providers do not allow big file attachments. ( e.g. files larger than 10MB). Even the App sends your files, but your email provider may remove the attachment due to size restriction. 

We do not recommend to send big files through email. Instead, we recommend to send big files through one of your cloud drives such as iCloud Drive, Google Drive, Dropbox, etc..