From personal experimentation, a gzipped base64 jpeg is close to the same size as the jpeg. So if you want to efficiently store some emails, it doesn't really

From personal experimentation, a gzipped base64 jpeg is close to the same size as the jpeg. So if you want to efficiently store some emails, it doesn't really matter whether you decode and store attachments separately or just compress the raw text. (Although decoding and separating allows deduping.)