I'm using Windows Live Mail. I am trying to send an e-mail to our supplier, but when I do, the e-mail sits in the outbox. This happens when sent to the suppliers domain from any e-mail in our domain (so me and any of my coworkers all have the same issue). However, all other e-mails sent to anyone else, all go through just fine.

The domain we're trying to send to has been added to our whitelist. I double checked POP and SMTP settings, which seem fine (and should be, since all other e-mails will go out).

I have no idea what the problem could be. The supplier says that our domain has been added to their whitelist as well, but I can't verify this. Would that be an issue? Are there other things I could try on our end?

Any help would be greatly appreciated. Thanks!