Thanks for reaching out! In SmarterMail 16.x, we introduced a new feature for forcing SSL. In each domain's configuration, you'll find a setting on the Security card for "Force all traffic over HTTPS". Please follow the steps in the article below, and let me know if this help to resolve the issue:

Force Webmail Traffic Over HTTPS

The reason for this is likely because the browser is having to sometimes load non-secure content in emails from external sources such as images. The website is still running over a secure connection. This is a tough challenge to tackle as in order to maintain this green lock or secure messages, we'd need to block external content that is loaded unsecurely, like images in an email. There are ways of maybe proxying images through the SmarterMail connection but this could increase bandwidth and load since now your server (not the client) would have to fetch and cache, then re-serve the images from itself replacing the links in the email.

Not saying this couldn't be done, it's just very challenging and is not something that we have yet figured out.

We are only up to SM v15, but I block all non-SSL traffic (besides port 25*) at the firewall (Sonicwall), keeping ports 80, 110, 143, and 587 closed to the outside world, so SSL is effectively forced, using ports 443, 465, 993, and 995. I'm not using TLS. My installed certificates for SM's protocols are x509, as exported from the installed IIS certs.

 

Folks going to [webmail.mydomain.com] are redirected to https://[email.mydomain.com] by zone file settings.

 

It all seems to be working pretty well.

 

Am I missing something?

 

*We filter inbound 25 at the firewall to only accept mail from the IP ranges of our smarthosts, Microsoft EOP and Symantec Email Security.cloud. Outgoing email is relayed through those hosts only, depending upon domain. 

is there any update on solution for issue where it says not secure with certain webmail email images ?

as mentioned above by Matt it looks like gmail uses proxy to tackle this... code when this picture is on gmail is a google proxy one vs the original that shows when inspecting the image in smartermail webmail