I installed the latest version of gpg4win which is v3.1.0. Also the GPGOL v2.1.0 plugin was installed in my Outlook 2016 installation. The e-mail address used in both Outlook and Thunderbird is the same and is going over Exchange server. When I send e-mail to other users with an attachment who use the Outlook/GPGOL combination, it works perfectly. But when people who use Thunderbird in combination with Exquilla (Exchange) and Enigmail, try to open the mail, the only thing they see is an empty mail with an attachment named gpgolXXX.dat.
In GPGOL I have set the option "Send OpenPGP mails without attachments as PGP/Inline" and in Kleopatra I've set the following option as an extra next to the default ones: "create signed or encrypted files as text files."
Would you know what the problem could be? What can I do from my side to test this further?