Slack include SIP URL in the message

I'm adding messages that includes url markdown to a slack channel using this format:

<http://somesite.com|friendly name> -> works
<mailto:[email protected]|friendly name2> -> works
<sip:[email protected]|friendly name2> -> url markdown doesn't works

When I use <sip://[email protected]|friendly name2> the markdown convert it to link but the sip client fails to connect due to the extra "//"

Any idea how to make sip links on slack?

Solution

Slack's documentation only mentions http/https and mailto schemes for automatic linking, but I played around with their message builder and noticed the following:

Schemes followed by :// seem to be generally supported
In addition there seems to be a whitelist of other schemes supported. The only ones I found working so far are mailto and skype.

While that matches your observation it looks like there is no way to have automatic linking for the sip scheme.

What you could do is to write a Slack App, which provides a command (e.g. /sip [email protected]), which will print a link to a website which redirects you to the proper sip-URL. I believe that's the approach other services like Zoom use as well for their Slack integration.

An interesting alternative could be to contact Slack and kindly ask them to add sip-URLs to their whitelist.