Rather than returning the direct mail call in the build method of a mailable you can assign it to a variable then add multiple attach calls before returning.
Here’s an example:
public function build()
{
//setup the mail
$mail = $this->subject('The subject', ['content' => $content])->markdown('mail.sendreply');
//loop through attachments and attach to $mail
$att = Attachment::where('sendEmail', 'Yes')->get();
foreach($att as $file) {
//attach the file
$mail->attach($file->filePath);
}
//return and execute sending the mailable
return $mail;
}