I realize this isn't really a Nintex issue but a SharePoint issue but I feel that you should be aware...
So I created a Nintex workflow to send emails but also BCC to a SharePoint library to keep a copy. Emails to recipients were working just fine but the BCC emails into the library was not.
I was able to send email from my Outlook client. Weird. I know other workflows are able to send into other libraries.
I changed the incoming email settings of the library, nothing worked. I soon realized that its not the workflow, but what was in the email subject line like this:
ACTION REQUIRED: Please confirm mailbox ownership of email@example.com
After many tries from Outlook, it stopped being received when I added the email address into the subject.
and SharePoint ULS Logs will show lines like:
An error occurred while processing the incoming e-mail file... The error was: The following file(s) have been blocked by the administrator
If anyone has an idea of how we can get around this, please let me know... otherwise, I'll be leaving the email address out of the subject line.
FYI - URLs in the Subject line does work. The URLs get modified with underscores.