I would have to assume that if you attached the file and noted in the subject and body of the email who you are and what you've attached, then there'd be no problems with the receiving party opening the attachment.
NOTE: There was a thread here not too terribly long ago where someone asked what type of file he should use to attach his resume. I said that using a .pdf was a no brainer due to 1) it's cross platform ubiquity, 2) it's ability to embed images and fonts to preserve the design and layout and 3) it's ability to disallow the receiving party to edit the file. Someone later posted, however, that they had information form someone reputable that a Word file was best... But what version of Word?! I dunno. I'd still use a .pdf.
It'd also NEVER hurt to include, *in the message body itself*, a plain text copy of the resume.
EDIT: Heck, you know a lot of people post resumes online, too.