Limitation of Attachment size when using SMTP

I wrote a C++ program to send a mail using SMTP. But when I attach any files I notices that a sin开发者_Go百科gle file's size always is limited to 808 bytes. As an example if I send a text file with 10 KBs, when I download the attachment it has only text worth 808 bytes. If the large file is a zip file, it gets corrupted in unzipping obviously due to CRC failure. I used a MAPI library to send larger files without a problem. Is this a network limitation of SMTP? Can someone please explain why this is happening??

Thank You!!!

How are you attaching and encoding the files? Are you using MIME? 8-bit clean?

SMTP has no built in limits, but has specific limits in how data is transferred (formatting, etc). In general, most mail systems reject mails with greater than 5-10MB of data.