We installed the RTM release of SharePoint 2016 and our offshore team had issues with outgoing emails not being sent in SharePoint 2016. We realized that it wasn’t just our product unable to send emails, the out-of-the-box SharePoint Alert emails were also not sent.
This eliminated the possibility of some bug in our code or SharePoint Object model change in 2016, so we started looking at our Exchange settings and SharePoint 2016 settings. We spent a couple of weeks figuring out if the issue was to do with some new setting in SharePoint 2016 or a combination of Exchange 2010 and SharePoint 2016. In our case it turned out to be both: Exchange setting and new requirements to enable TLS encryption. I am writing down our experience in fixing this issue here, so it may be helpful to someone who faces a similar issue.
Receive Connector in Exchange
The emails were working in our US office, so we thought there was some setting in the Exchange that was causing the issue. We got help from our IT admin and he asked us to check the Receive Connector in Exchange. In our office, it was enabled to receive outgoing emails from our SharePoint servers. We forwarded the Configuring outgoing email in SharePoint 2010 with Exchange 2010 – Step by Step Guide to our offshore IT team and they created a new receive connector in Exchange to include the new SharePoint 2016 server’s IP address.
Some settings we had in our working Receive Connector.
SharePoint 2016 SMTP Encryption requirements
Even after adding a receive connector, the emails were not sent. Then we started playing with the TLS encryption, via the new setting that was added to SharePoint 2016 outgoing email settings page and found that when we disabled the TLS encryption the emails were going out.
Then we looked at the SharePoint 2016 SMTP Encryption requirement and found that we needed to enable STARTTLS in our Exchange, have valid certificates, and have TLS encryption supported. Once we
enabled TLS encryption and STARTTLS we started receiving emails.
This is how we got our emails working on SharePoint 2016 server. I hope this proves helpful to someone out there facing similar issues.