is there any way to increase email attachment limit

No. Use a service like dropbox and send the link of your file to your recipient.

http://support.apple.com/kb/PH2629?viewlocale=en_US

Important: An iCloud Mail message can’t exceed 20 megabytes (MB), including attachments. If you use an email program (instead of a browser), a message smaller than 20 MB might still be undeliverable. Your Internet service provider (ISP) may also have message size limitations. If a message is returned to you because it exceeds the maximum size, send the contents of your message in multiple email messages, or use compression software, such as the Compress feature in OS X, to make your attachments as small as possible.

I'm afraid not. This sort of limit is applicable on most emails services. If you want to send large files regularly you should investigate file sharing services such as DropBox (which can make files available only to authorised people).