(Last updated 27 Nov 2020)
Sometimes LUGgers ask me questions about email oddities, and I'm not very good about answering. Here are some Frequently Asked Questions that are not (alas) Frequently Answered. I will try to update this periodically as new questions come in.
Q: I sent a message and it bounced back with the comment that "The message's content type was not explicitly allowed" or the more dire-sounding "The message's content type was explicitly disallowed". Huh?
A: The short answer is that you probably used Outlook to forward a message to the LUG, and that combination is toxic. Sending a new message works fine; replying to a message works fine. Forwarding a message often doesn't work fine when Outlook is involved. To bypass this problem, create a new message and copy/paste your text into it. To understand this problem, keep reading.
Always read error messages carefully. They often tell the truth. On this one, you need to note that it says "content type" and not "content". The content type is something like "JPEG image" or "rich text with many fonts and colors". It is not complaining about the content, but about the type of content. Often, though, error messages are written by software engineers, and the vocabulary is hard to comprehend. This is one of those times.
There are dozens of different content types that can be sent by email, and the LUG mailer ignores most of them. Examples of content types that will get ignored if you try to include them are video clips, sound recordings, apps, and (strange for a photography forum) images. You can send text, or you can send text. If you want to include an image, upload it somewhere and put a link to that somewhere into your message.
All of this email stuff was invented when Harold Wilson and Edward Heath were Prime Ministers of the UK. Gerald Ford and Jimmy Carter were the US Presidents. The inventors of email were remarkably clever engineers and remarkably poor fortune tellers. They envisioned a world that was much more technologically varied and complex than what we actually live in, and they designed email systems to be really flexible.
Because of the excessive flexibility in email system design, it is possible to create impossibly complex content types that no sane person who knew what "computer virus" means would allow on her computer. This is where Outlook enters the picture. Microsoft has always worked to keep its systems compatible with the past, even when that past is long gone. If you are sending From Outlook and To Outlook, it can always avoid falling into traps of its own making. But sending From Outlook to something else is fragile because Outlook was designed to communicate only with itself. If Outlook generates complex madness, it can remove it at the receiving end. Other receivers are left to fend for themselves. Most non-Outlook systems (including the LUG software) protect themselves against unknown chaos by rejecting it.
Brian Reid