Nothing to be sorry about. There is no rule about posting an email address in this forum. It is really more of a safety/privacy concern than anything else.
The problem is that anyone (not just SC4D members) can read these forums. Once you've posted an email address publicly, anyone can use that address for whatever nefarious use they choose (including making that address essentially unusable to you). At least there is some small recourse if a member abuses your email address.
There are many methods for other members to communicate with you (to include email if you allow it in your profile), without you having to publicly post your email address.
This is really just part of practicing safe Internet.