Campaign emails not delivered but preview test email works fine

[NeilP]

Hi ... I have a user who is not receiving email campaign items, yet I can send them a preview without problem (same email) so their own email is not blocking / filtering (unless the preview engine is different from the campaign engine).  The campaigns are being received fine by ~800 other users.  This is a key user in our organization, so I need to get this fixed.  Any help / suggestions on how to troubleshoot are much appreciated. 

[Caitlin_M]

Hi @NeilP. If this isn't happening for all contacts, it's best to work directly with that contact as they may have a security setting under their email client or security program that is preventing them from receiving the email. You can have them safelist our URLs and IP addresses in their security program and safelist your From address as well.

[NeilP]

Hi Caitlin ... thanks for your reply.  We are using Office 365 and many other users (myself included) are successfully receiving the campaign emails.  Because of this, I doubt that safe listing URLs / IP addresses will help.  Also, the user in question isn't even receiving them in her junk folder.  Yet when I put her same email into a campaign preview, it sends just fine (arrives into her Inbox normally).  Do previews get sent from a different source within Constant Contact?  How could those emails be received ok but campaign emails not received at all?  Is there any way to trace something from the Constant Contact side?  

Thanks in advance.  

[William_A]

Yes there are different sending elements associated with test sends versus live sendouts, especially in regards to authentication. On the contrary, if they specifically aren't receiving the emails, safelisting is the next step they should take to ensure their system isn't erroneously blocking the emails altogether. 

If they're unable to resolve the issue from their side after safelisting your sending address and our domains, then I'd advise reaching out to our Delivery team for any further insight they may be able to provide regarding that particular contact (or their network).