My company has a policy stating I do need to inform manager - so my first internal (lateral) move, I did notify manager - she appeared supportive, even said she would talk to hiring manager on my behalf, and get back to me. Then poof, never heard from HR regarding my application, never heard from hiring manager and worse my manager never communicated with me. I was terrified for a month I had set myself to be fired. So then I applied for position #2, I marked the HR application that I did tell my manager I was applying (I did not, as I figured our previous conversation in job #1 application did include me stating, even if nothing transpired, I would continue to keep my eyes open for future opportunities within the company - it is a very large company). So I interviewed, 2 sets with 4 people. Then I had feedback from other managers that they would love to see me in this new position. Then I had follow-up with one of the higher management team and they asked me directly am I still interested in the position. I said yes. Then silence due to travels/meetings, etc. About 3 weeks later I get an email from my boss, "Ok- so you might have mentioned this the other day...." and attached to it was an email from hiring management that they were going to extend me an offer (This was the first I heard). But I tired to send an email explaining, but current boss was throwing a tantrum and sending very stern emails to me. Whatever I was saying just continued to upset her. So finally I sent her an email stating basically, I was planning to sit with you if an offer was received....you shared a confidential email with me, as I was not aware of the pending offer. At least she stopped with the emails. After my first experience, why would I tell her about my continued applications internally? She definitely was not supportive, and seeing the emails she sent me on learning I had interviewed, I know I did the right thing - she was not going to be supportive in my search or my goal for growth within.
With that being said, I did work in a separate company once - I had a great manager, who encouraged me to look to grow after a few years with the team. I am so appreciative of his nudges, I would have never gone outside my walls of security without his encouragement. To this day, I still use him as a reference in any job searches I do. (YEARS later).
My 2 cents: know your boss, and trust your instincts.
And yes, I have told some office workers about the email exchange, their advice was to AFTER signing on the dotted line if presented, forward the email chain to HR...if I do not get, still send to HR - my boss broke confidentiality. I don't know if I will actually do that (not my style, as I believe in karma) but I am still shocked by it all.
Good luck to any and all who are in job searches.