Question: Quick question for the Sims 2?
My sim has made like 7 friends already for his job, but I can't keep calling them everyday. Will e-mailing them everyday keep their relationships up?
Answer:
Email does improve relationships, but not nearly to the extent phone conversations do. You get around 1 point per email, and then you have to check back for responses. By the time you get done with the repeated emails you may as well have used the phone. It works well for contacting friends with work hours that conflict with the character's off-hours.
Personally, I don't usually keep the relationships up and they still manage to get promotions. Just give people a phone call every few days and it should be fine. If phone calls take too much time then cut them short or take turns deciding which friend to call. Or maybe invite them all over, since face-to-face interactions work just as well. You also might consider inviting them to the community lots, since it pauses time at home when you leave it.