Export not completed if many messages are non S/MIME

[kappapiana]

Apparently, if you fail to uncheck "include subfolders" and actually many non S/MIME messages are exported, the plugin fails.

Of course, you should not preserve non-S/MIME messages, as they are not signed and need not to be included in the process.

I suggest to un-select "include subfolders" as default value.

[alpianon]

tried in many ways (f.e. backing up a folder with 400+ S/MIME messages with a subfolder with 223 non-S/MIME messages) , but I cannot reproduce the error (while trying, I have found - and solved - issue #14 but it was another problem; in your case, backup does not even finish, does it?)
Could you reproduce the error also on other PCs?

[alpianon]

Implemented a workaround, that disables "search in subfolders" option when selecting PEC backup, see commit 286c9e6