Bugzilla

This bug is   not   a duplicate of bug 180769.

This bug arises from the fact that Thunderbird does not follow this long established principle: data confidentiality in transit and data confidentiality in storage are distinct requirements and call for distinct implementations. 

The result of this bug 188988, is this: if a message was encrypted in transit, Thunderbird can't search the body of that message.

bug 180769 arises from the fact that that the dialog for Menu>Edit>Find>Search Messages includes many choices of what to search for, but does not include "Encryption Status." 
This has nothing to do with the fact that twenty years ago Thunderbird's choice was to implement data confidentiality in storage for encrypted messages by storing the message in its encrypted form.
The result of that bug, 1807679, is this: Thunderbird can't search for messages that were encrypted in transit.

bug 180769 may not be a bug  In this sense: The choice, Menu>Edit>Find>Search Messages>Match>Subject>Customize..., allows the user to add other message headers to the choices in the list under Subject.  For example, searching for Content-Type--contains--smime would do the job. (Or the corresponding text for an OpenPGP message.) 
The Thunderbird experts will know. 

I could check that in a minute.  But I must go attend to something else.  I'll post a general comment on this bug later.
Meanwhile: I do not have permission to change the Status of bug 180769.  
Someone please do: thank you!