7. Use the same method to add updated versions of files. When prompted, click Yes to confirm you want to overwrite. Note that when you add files to an archive, 7-Zip compresses them using the Fastest level, regardless of the level originally used for the archive.
8. Many email providers enforce attachment size limits. When sending lots of files - or one enormous file - you could come unstuck. 7-Zip lets you split archives into multiple parts. Under Split to volumes, simply enter the maximum size, appending K for kilobytes or M for megabytes.
9. When you split an archive, 7-Zip will append each part with .00x (where x is the version number). The recipient needs to extract only the first version of an archive. The remaining parts will be automatically stitched together. The recipient will, however, need 7-Zip installed on their system to extract the archive.
10. Archives can be encrypted. This is useful when emailing sensitive data to someone who uses a shared PC, for example. To encrypt an archive, simply enter and confirm a password. For the encryption method, we recommend 256bit AES. It's an established standard and virtually uncrackable.