diff -urN ../exim-4.96.orig/src/rfc2047.c ./src/rfc2047.c
--- ../exim-4.96.orig/src/rfc2047.c	2022-06-23 16:41:10.000000000 +0300
+++ ./src/rfc2047.c	2022-06-29 21:49:36.191006000 +0300
@@ -114,7 +114,7 @@
   continue the loop to search again. We must start just after the initial =?
   because we might have found =?xxx=?xxx?xxx?xxx?=. */
 
-  if ((lencheck && *endptr - mimeword > 73) || *q2ptr - *q1ptr != 2) continue;
+  if ((lencheck && *endptr - mimeword > 148) || *q2ptr - *q1ptr != 2) continue;
 
   /* Get the encoding letter, and decode the data string. */