diff --git a/lib/imapoptions b/lib/imapoptions
index fd9d4abe461..c02516936bc 100644
--- a/lib/imapoptions
+++ b/lib/imapoptions
@@ -3063,7 +3063,7 @@ product version in the capabilities
 
 { "tls_server_dhparam", NULL, STRING, "3.1.4" }
 /* File containing the DH parameters belonging to the certificate in
-   tls_server_cert. */
+   tls_server_cert. Used by OpenSSL before version 3.0. */
 
 { "tls_server_key", NULL, STRING, "3.1.8" }
 /* File containing the private key belonging to the certificate in