Send Executables as Attachments in gmail, yahoo, etc hotmail,

When you receive an e-mail from an address that doesn’t end in @gmail.com,
Gmail looks at attachments for file extensions known to be executable (such as .dll, .exe, .vbs, and so on), so if someone sends you one of these file types, their
message will bounce back.

I am taking example of gmail.

This goes for files within ZIP archives as well—Gmail looks inside these for executable extensions and the e-mail bounces back to the sender if it contains any.

Gmail doesn’t look inside other archive formats, such as RAR or ACE, so you might want to use one of these formats instead of going through the hassle of the following workaround.

The trick is very simple..
Simply tell the sender to rename the extension of the file to something
Gmail will allow (such as .jpg), and when you receive the file, rename it back to
the type it really is (for example, change file.jpg to file.exe).

Enjoy :)