My synapse has always been working correctly, and I am using it's ssl in my current project. But today when, motivated by this thread, I tried to compile the XMailer package I must have broken something somehow- same error message as in the first post: "unit ssl_opernssl not found". So I had to investigate...
The problem is that the the ssl_openssl.pas file is found in the synapse installation folder, but it is not included in the laz_synapse package, probably because they wanted to keep the stuff which requires external dlls should not break the non-ssl usage of the library if the dlls are not found. That's a good idea but poses a massive problem when another package or a project requires the ssl_openssl unit. Since the compiler knows only the path to the compiled package units it does not find the sources of the ssl unit.
A possibility to solve the issue is to add the path to the synapse sources to the unit search path of the project or package, as the Delphi people are doing. I refrain from this because it ties the project/package to a given directory structure. And it can be the source of other compilation problem.
Another solution has been mentioned already above: Open the laz_synapse.lpk file in "Package" > "Open package file", click on "Add" > "Add Files from File System" and select the ss_openssl.pas file. Click "Compile", and the XMailer should be working now. What I don't like here is that a third-party package is modified here, and that any usage of the synapse library must find the ssl libraries now.
Here is another, less intrusive solution: Create a package, maybe laz_synapse_ssl, which requires laz_synapse and contains only the unit ssl_openssl. When this package is compiled (no need to "install") and is in the requirements of a package/project the IDE knows where to find ssl_openssl. I am attaching the package file which must be saved in the same folder as laz_synapse.lpk.
Now only the new package must be added to the requirements of a project/package requiring ssl. Other usages of synapse are left untouched. While this solution does not modify any synapse file it requires modification of the XMailer package because the new package must be added to the requirements. And it should be mentioned that two packages residing in the same directiory is a somewhat unstable situation - in my tests it works, though. Nothing's perfect...
I am attaching also a modified xmailer package file adjusted for the latter solution. It must replace the original one.
Unfortunately, the synapse project seems to be pretty much dead, and I don't know how to contact the authors to get this issue fixed properly.
[EDIT]
Please read my next post for a better solution with the laz_synapse_ssl package.