'Unwelcomed' doesn't apply anywhere. You can be 'unwelcome', as someone whose presence or company is not wanted or desired. 'Unwelcome' also applies to a comment uncalled for. 'Not welcome' applies to a forewarning to undesired visitors or to comments that might be made. Once you have been welcomed you can't be 'unwelcomed', although you can be thrown out if you make yourself unwelcome. (Refer: 'unwelcome', Oxford concise English Dictionary - the same will probably apply to Websters).
Of course there is the outside chance of someone who's arrived at a venue/party, who has escaped the host's attention and has as such been 'unwelcomed', although by and large we'd say 'not yet met and greeted'.
What you are attempting to do is turn an adjective into a verb. Not that this has never been done, but it is unwise in this case. Unwelcome is what someone is or was. "Unwelcomed" would imply that someone who at some point was welcome, somehow lost that characteristic.
The notices we see in store fronts saying, "salesmen not welcome," could be worded "salesmen unwelcome" without changing the meaning at all. Salesmen who [are] not welcome are definitely unwelcome. But if you try to turn that last adjective into a verb it doesn't work out so well. First, there is a problem with the tense. If it were actually a verb, unwelcomed would clearly be past tense, so you would be describing something that has already occurred (and may no longer be the case). And then there is the confusion factor. Since there is already a good way to say that you don't want someone around (or--past tense--didn't want them around), this new word serves to confuse the reader. "Is there some meaning here that I don't understand? Is this the same or different from saying 'not welcome?'"
The exceptional authority on language, Bryan Garner (Garner's Modern American Usage) would probably call this a needless variant.
There definitely is a word "unwelcomed". It is an adjective, but having said that, I don't think I would have used it. It is somewhat clumsy. "He was not wlecomed" would be a nice way of getting around it. Yet "An unwelcomed bout of 'flu' (influenza) created a poor situation in the work force" scans better than “A not welcomed bout of 'flu' (influenza) created a poor situation in the work force" Ah! The English Language. What mazes and labyrinths it drags us down.
Don't be unfriendlied. I was pointing out that this was my view of the word: one that had arbitrarily been assaulted by an 'ed' that looked entirely foreign and …um, unwelcomed. …making it look entirely uninterestinged and unpalatabled.
Yes i'm getting very confused. I'm writing an article about being welcomed or not. eg "visiting new neighbours" the difference between being welcomed or not welcomed. Like having the door slammed in your face when you knock on the door.
I think I might tell the person that they are being 'intrusive' or, if less direct, say 'it's inconvenient.' 'Not welcome' or 'unwelcome' would not be the first words that spring to mind if I was trying to say it to someone, face to face.