For my online business, I need to send emails to my customers. Sometimes they get rejected by their spam filter. I try to encourage my customers to add my email address to their address book.
Do you think it would help if I attached a vcf file with my contact details? It would make it easier for my customers to save my contact details but at the same time it means that all my emails would have an attached file.
Is it a bad/good idea?
Sorry but no, adding a VCF with your contact information doesn't help your emails to go through spamfilters (i.e. be classified as 'ham').
I think you should split the question into two parts, there is the "content" side, i.e. how to lay out the message content so that it looks legit, and there is the "server config" site, i.e. how your servers should be set up.
I actually only know about the latter part, the server configs. And I don't feel it appropriate to discuss it here, it's IMHO off topic. (And if you search around on Serverfault.com & Stackoverflow.com and you will see it very well described there.)
While I don't want to discuss the technical aspects of server configuration here, it may be useful for others if I write up a short list of what needs to be done. Here it is, make sure that:
Mailchimp is a no go - they insist on using vcf: http://kb.mailchimp.com/article/can-i-remove-the-vcard-vcf-information-from-my-confirmation-emails