If the employer does not accept attachments—or they do not specify how to send your cover letter—it's best to simply copy and paste your cover letter into the body of the email. This way, the hiring manager will see your cover letter as soon as they open your email, instead of having to download an attachment to view it.
Once you've pasted your cover letter into the email body, remove the date and contact information from the top left-hand corner. Double check that your email displays properly since sometimes copying and pasting content from a Word or PDF document can skew email formatting. Use the default font and styling of your email program.
Don't forget to add the proper email signature to close your email and make it easy for the hiring manager to get in touch with you. Your email signature might look something like this:
First Name Last Name
Email address
Phone number