This is a post/support ticket I posted on the SMF forum. It's a bizarre problem and I am obviously not the first person to report an issue with using the word "from" in some longer posts. I found this exact issue going all the way back to 2009. i am just posting a copy here for reference.
AJ
I have been running a board using SMF 2.0.15 Since mid-December and it has worked great. I've noticed on rare occasion when I post a fairly long post, but not longer than the 40,000 char max I have set in settings, the server will throw up an "internal server error". The complete error is down below.
After careful troubleshooting I isolated the problem to the word "
from". Regardless of where I place this word it causes the error. If I change any of the characters in the word "from", even a single letter to upper case, then there is no problem.
If I create a simple post using the "
from" word only there is no problem. In longer posts it does not matter where in the post I place the word "
from", it will cause the error.
Here is an example: The first post on this page has a few instance of the word "
frum" in it. If I change ANY of those to "
from" it will not post, but will throw the error.
URL - galactichub[dot]com/CapsForum/index.php/topic,76.0.html
I did a search on this problem and found the exact same problem from 2009 in this thread.
Internal Server Error By Using "from" Word in Post
« on: November 18, 2009, 05:16:27 AM »
https://www.simplemachines.org/community/index.php?topic=348813.0;nowapI do hope this can be resolved. This is sure to frustrate some users.
Below is the complete error. There is nothing in the log. Again, this is a very clean install.
Internal Server ErrorThe server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at webmaster@aims-association.org to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.
Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.