Gmail is almost always reliable when it comes to attachments, but on the odd occasion a file or image you've sent is corrupted, you do have an option that essentially guarantees no problems — uploading to Google Drive first.
Image: Cairo / Flickr
As gHacks' Martin Brinkmann shows, it's incredibly straightforward to insert Google Drive files into your Gmail emails.
This does require you to upload the files (or files) to Google Drive, but this isn't that different to manually attaching them to the email and hitting send, as they have to be uploaded anyway.
By using Drive as an intermediary, it doesn't matter if the email is mangled or otherwise corrupted; the files on Drive will be unaffected, meaning you can just resend the links.
Of course, if you're regularly sending bulky files via email, it might be wise to look at options such as an FTP server or Dropbox to streamline the process.