Hi @patricks, it's a great question,
Here are some ideas:
1. Start with a topic-focused channel
SharePoint deployments can be massive and people can get lost in all the different sites and subsites.
Having a project-centered Mattermost channel with links in the header to all the reference sites lets you focus on getting things done, rather than setting things up.
For example, if you're hiring, you might have an applicant tracking system, a college campus recruitment schedule, and interviewer training materials across different systems.
You can create a channel for discussing recruiting overall, with links to SharePoint and other systems using markdown, to have a discussion all in one place.
The problem with email is that when you say "Hey Sam, I can't make the interview screening session at City College, can you take my place?" you'd have to link to three different sites for Sam to have all the information needed to say "Yes".
When everything vital about recruiting is in a channel, it's a lot easier for new people to get started.
You can even overload headers to share a wide array of links, or even timelines and due dates:
2. Try Mattermost for onboarding
When someone is new to a process, like recruiting, you can add them to a Mattermost channel for them to read through past discussions and get a feel for process without having explicit training.
This can start a cycle, the more people learn a process by reading through Mattermost history, the more people want to use Mattermost to train others.
3. Start with email-based integrations
If you're on-premise only there's open source mail integrations like mattermail and jstuart you can use to incorporate updates from SharePoint without custom development.
We'd love to see a SharePoint-Mattermost integration as well, if anyone in the community is interested in providing one.
If you're okay with using some SaaS-based integrations, you can setup Zapier to parse emails and output markdown-based posts to Mattermost:
There are just starting points, would highly welcome thoughts from other Mattermost deployments in environments where SharePoint is also used.