[Grammar] by mistake/ mistakenly

[shibli.aftab]

Which sentence is correct?
1. That message was sent by mistake.
2. That message was sent mistakenly.

Thanks

 

[Barb_D]

Which sentence is correct?
1. That message was sent by mistake.
2. That message was sent mistakenly.

Thanks

#1 is fine.
#2 would be more natural (in my opinion) if you changed the order to be "mistakenly sent" (and would be a second choice to #1)