I have been working on a project with a collaborator for several years. I have never met my collaborator in person but we've been a part of weekly calls and sent hundreds of emails together so I feel like at this point I know this person fairly well.
In what seems like hundreds (at least 10's) I have noticed my collaborator always misspells "a lot" as "alot". This person is my senior (he's a graduate student, I'm a pre-doc) and I am wondering if I should let him know in a polite way that he is making a common misspelling. It does not particularly bug me or anything, and I am not a particularly fantastic speller myself, but I just want to help him out in case he doesn't know already. Does it make sense to bring this up with him as a colleague or is this not my place?