getting mail delivery failed messages i didnt send

is this because 1 & 1 dont use spf records?

[lethal0r]

im getting an increasing number of emails with the subject 'Mail delivery failed: returning message to sender'.

now i didnt send these, so am i right in presuming ive been put as the reply-to on a spam email?

i use 1 & 1 for this particular domain, who dont use spf. if they did use it would that stop me getting such emails?

[bill]

SPF itself doesn't stop these mails. It just gives you something to filter by. If your filtering system takes the SPF information into account you can catch mail like this before it reaches your in-box.