I don't need a tutorial on what the acronyms stand for. I know what they are but am not clear on the details. SMS (short messages phone number<->phone number) is for users on the same carrier and it's plain text and free. I get that. The part that I'm not clear about is MMS. It's basically like regular email long email and you can send videos/photos etc. Why does SoftBank have their regular firstname.lastname@example.org addresses and also their email@example.com address? I know that the firstname.lastname@example.org is the regular extension for mobile phones and that email@example.com is for their MMS (which you can also check online using a PC), but MMS is not free (even when you have the unlimited data plan). You have to pay for every MMS if you're sending to people who aren't using SoftBank mobile phones. Which means there is no reason for them to have the firstname.lastname@example.org address. Why would anyone use that email@example.com extension when it costs money for each MMS message and when you can use SMS (messages via phone number) with people on the same SoftBank network. Even when you're sending to other SoftBank users MMS costs $$ when you send photos/videos so why would you use it when you can just send images and photos via regular iOS Mail app (firstname.lastname@example.org)? ** As a side note, I can check my email@example.com mobile email via OS X Mail app on my iMac no problem. I just entered in the IMAP details and bingo. If I'm away on holidays etc I can check my emails sent to my mobile phone which negates the need for MMS even more. Lastly, if we're paying 4,00 yen / month for unlimited data shouldn't all MMS messages be free? A bit confused.