I need to send e-mails to invite people to an event where they have to register in advance on a website. The website is accessible via a link that necessarily contains upper case letters. (I cannot change this!)

Details: The link is http://vhs.link/PraSpra19

This address does not work when spelled with only lower case letters in the path part of the URL.

When I create my e-mails in Thunderbird, everything is fine. I can type the link as above with mixed letters, and it will be used in that very form.

However, when I do this in Outlook (which I am forced to use at my workplace), Outlook annoyingly transforms all upper case letters into lower case letters. It does this not on the surface (the readable URL remains untouched!) but it does so in the actual link - with the wonderful effect that the link does not actually work any more. (It leads to a wrong place, the home page of vhs.link, instead of the sub-folder where it should lead to)

I was hoping I would find in Outlook some hidden setting to switch this idiotic feature off, but I did not find any. Of course, I also tried to manually post-edit the link. However, capital letters will always be replaced by lower case letters, what ever I do.

Is there a solution?

(I am using Outlook 2016)

More observations

I tried to switch off in Outlook all auto formatting settings related to links (thats: File --> Options --> E-mail --> Editor options --> Auto correct --> Autoformat [and Autoformat while typing]).

The effect is for sure that link text is not any more automatically given link funktionality, and accordingly I have to give them the "link" feature manually. (Which is okay).

I am not yet sure, however, about the effect on functionality. Actually it seems that these links do indeed work now (i.e. the upper case seems to be preserved somehow). What is a bit disconcerting is that in the popup field that shows the underlying link when you mouse-over the visible text, the link is still being displayed as lower-case only. That's a bit weird.

  • This is because the site is hosted in Apache, which is case sensitive. Are you able to move it to IIS? Other than that, change outlooks automatic formatting off. – spikey_richie Sep 9 '19 at 17:48
  • @spikey_richie I am unfortunately not able to change the site's underyling technolgoy, as it is not mine. (By the way, if I had access to that web server, I would simply set the folder name to lower case, which would solve the entire issue easily.) What I need is a solution how to stop Outlook doing these case alterations. - I am going to test your suggestion with the auto format settings. – Christian Geiselmann Sep 9 '19 at 18:02
  • @spikey_richie: As per RFC 7230, paths in HTTP URLs are supposed to be treated as case-sensitive by default. The webserver can choose its own rules for mapping URLs to resources, but external applications (such as Outlook) are in no place to enforce case-insensitivity on random URLs they encounter. – user1686 Sep 9 '19 at 18:05

PREFACE: I had the same issue when sending emails with a unsubscribe link at the bottom. This link had a secure query parameter for identifying the user. This parameter has to be signed to prevent tampering, and my signing tool (Ruby on Rails' MessageEncryptor) outputs a combination of upper and lower case letters. Outlook users who would click on the link would get an error when the server could not decipher the parameter, because the uppercase letters had been swapped by lowercase ones.

The Solution:

I URL escaped also the uppercase letters! i.e. changing 'A' to '%41', 'B' to '%42', and so on. Reference.

This worked surprisingly well in my case.

In your case this would mean changing this http://vhs.link/PraSpra19 to this http://vhs.link/%50ra%53pra19 .

In Ruby this is what my solution looks like:

  def url_encode_caps(s)
    s.to_s.b.gsub(/[^a-z0-9_\-.~]/) { |m|
      sprintf("%%%02X", m.unpack1("C"))

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