Using the replyto: field as a filter in mail.app I've been getting spam that has one thing in common: all the mails have a reply-to field of the form: replyto1@&lt;domain&gt; where the domain changes from email to email. 

I'd like to set a search to filter these, but from looking around it appears that mail.app cannot filter based on the reply-to: field. Is that correct ? Is there any way around it ? 

I'm running the latest update of Mavericks.
It is possible to search by the Reply-To filed.

In the email go to the reply-To filed hover over it till it becomes highlighted.

There is small down arrow next to it.

Click on it and new window opens allowing you to search by that Replay to field.

Here is what it looks like on my MBA.



It will only search for the part before the @.