I can only speak from my experience. But you may send one but there are various other fellowships doing exactly the same thing, so when I log on I have a few invites at my shield. The higher my ranking the more there are. So it may not be your intention to spam the player but often the invitation gets lots among others, as they are really all anonymous and there is no real differentiation.
The player that sent a message and followed that up with an invite got my attention. The rest I deleted on sight, as the perception is that the only reason you are inviting me is to make up numbers in your FS, because you need my goods or because I am a higher ranking player. Those all benefit the faceless player inviting me - but what is in it for me? I have no idea what your FS is about, why is it better than another, why do you have an opening - is it because the FS is not player friendly? I just tend to steer clear. A personal touch goes a long way
Remember, not all new players know, or fully understand the benefits of fellowships, so invites get ignored out of ignorance too.