Hi
I developed a workflow which looks for number of attachments in a mail and performs a particular activity if number of attachments are more than 1 and another activity if number of attachments are equal to 1.
I’ve noticed that for few mails even though there is one attachment it is going to the workflow block with more than 1 attachment , this i noticed when the mail is forwarded multiple times.
May be those mails will have some images in the signature or background part. That may come as attachments, so your count become incorrect. Check that as well. Try to check the attachment with its extensions.