Is it alright if I maintain a personal contact with a specific user? There is a user who I've found to be particularly meticulous in writing proofs. I am learning a couple of disciplines on my own and frequently am faced with the need to post (solution-verification), (proof-verification) questions. I have a contact with the specific user and is it alright if I send him a link each time I post something and ask him to check it out for me? I vow to aknowledge and give preference to answers by other users if they are better. What would be the site's policy on this situation?
I suppose that at this point, I should just write an answer.
On Feb 17th, I answered a question of Ishfaaq's, shortly thereafter received a very polite email from him asking if he could email me whenever he posted a question. I assented, and since then, he has emailed me asking for help on two other questions. This works out to him asking me about a question a week, a pace that I am comfortable with.
Of course, if the pace were to significantly increase, or if many other users were asking for a question a week, or if I got the impression I was doing someone's homework/take home test/ etc, then my attitude would change, but as I said in a comment above, I purposely have my contact info available in my profile.
Why do I do it? The same reason I've spent so much time on MSE - I enjoy helping people learn math. Sure, I ask the occasional question (12 on this site so far), but I much more enjoy answering questions (316). As Will Jagy mentions, proof verification is not my favorite kind of question, but I really appreciate the fact that Ishfaaq's questions (or, at least the ones he has emailed me about) have a lot of work shown - he is putting in more effort than many of our users, and I want to reward him.
Finally, I just want to note that this a personal post and is in no way intended to reflect or persuade the MSE community at large. It's simply how I've chosen to deal with emails. In general, I don't see any issue with a particular user attempting to contact another user via email, but I also don't see any issue with the other user ignoring the email completely.
There is no rule against contacting other users outside MSE. The only exception would be if someone harasses another user in relation to MSE activity, which I would consider in some cases to be legitimate grounds for a suspension.
But not everything that is not forbidden should be done. When a person answers questions on MSE, the person can decide which questions to answer and when. Asking in, say, an email can put some pressure on a user.
Personally, I would only contact another user outside MSE in exceptional circumstances or if I know the person outside MSE. In that case, standard real world manners apply.
I get a few legitimate requests a year from graduate students. If it is in my field I generally answer. If there are too many contacts from one person, I arrange contact with the faculty adviser; that happened recently. It turned out the adviser was alright with it, so I continue to guide; at the same time, I do not want to have much contact, and I refuse to step between student and adviser. (note that the spelling is usually advisor, like doctor. it's wrong, but it's usual. Advisory is a real word).
On the other hand, a week or two ago I got a question from someone who wanted me to rewrite an optimization problem roughly in the area of linear programming. From what I could see, I was picked because the question had the phrase "quadratic form" in it. He then sent a heavily edited pdf, where no question could any longer be discerned. Clearly some attempt to cheat, possibly a test, term project. I really disliked the whole experience.
In particular, I don't want to proofread work by others. I do that enough for published articles. I'm guessing Jason is polite, but I find it hard to imagine that he wants frequent contact for the purpose of checking your work. What does he get out of it?
EEDDIITT: have you asked him (Jason De Vito) about this?