Adding a file attachment to an email is very easy and there is always a menu option or toolbar button to select a file on disk. Some email programs even support drag and drop. It all goes horribly wrong if you try to attach an executable program though. You cannot send someone a utility program they need for example and the email program will reject it. There is a solution though.
Some people may never have come across this problem because we rarely have to email executable programs, but sometimes you do and then you hit a wall. Create a new email in Gmail and you can drag and drop a program on it. When you try to send it though, you'll just get a message stating that it can't be sent. Outlook.com won't even let you attach an executable program, so you won't get as far as Gmail.
This behaviour is by design and it would be a security risk to send executable programs by email. Someone could send malware for instance. You might not even be able to send one within a zip archive. This clearly affects .exe files, but other file types can cause problems too, such as .reg files that modify the Windows registry. These may fail to send too. This means you can't email someone a registry fix, for example.
The solution is to send a link to an executable file. You can upload the program to free online storage and then share it. Get the shared link and then paste it into the email. With Dropbox for example, you can share files directly from the disk drive. Just right click a file in an Explorer window and select Copy public link:
Click in an email and press Ctrl+V to paste the link in the message. It isn't the only service you can do this with and there are other online storage and sync services you could use. It is definitely the way to send executable files though.
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