core-bundle/src/Resources/contao/library/Contao/Email.php
public function attachFile($strFile, $strMime='application/octet-stream')
	{
		$this->objMessage->attach(\Swift_Attachment::fromPath($strFile, $strMime)->setFilename(basename($strFile)));
	}
public function attachFile($strFile, $strMime='application/octet-stream')
	{
		$this->objMessage->attach(\Swift_Attachment::fromPath($strFile, $strMime)->setFilename(basename($strFile)));
	}
Attach a file

@param string $strFile The file path
@param string $strMime The MIME type (defaults to "application/octet-stream")