11-06-2015 12:28 PM - edited 11-14-2015 07:07 AM
I haven't seen this problem since ~2008
but encountered it again on ACT v17.1 HF6, Windows7, Office 365 (Outlook 2013, exchange email)
The problem: when emails were sent using ACT email merge (Write menu > Mail Merge), any attachments to that email was received by some recipients in a "winmail.dat" format. Those recipients seemed to be on public email domains, e.g. @yahoo.com or @gmail.com, etc., but that was not always true.
Proposed solutions: several sites described this problem but no solutions worked.
The work-around: In Outlook, if the default Address Book is set to the local ACT database, set it back to Outlook's default "Contacts" address book.
Then also clear the auto-complete cache in Outlook.
If you need to be able to address Outlook-originated emails to ACT recipients (by clicking the email's "To" "CC" or "BCC" buttons), setup sync between ACT and the Outlook Address Book