Hello @BjornS ,
You can use the search function in your contacts to search by domain (i.e. yahoo.com and aol.com).
Ultimately, the issue seems more tied to you having your own domain, but not using self-authentication. Due to Yahoo and other email clients' recent changes to their anti-spam algorithms, this can cause delivery complications. I'd advise checking out our Email Authentication FAQ - for guidance and insight on how best to setup your account's email authentication.
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