I am an obsessive email archiver, which is why I get so upset when people send multi-megabyte attachments over email (I much prefer it when people use services like [YouSendIt](http://yousendit.com) or [DropBox](https://www.dropbox.com/referrals/NTY3ODc2OQ)). There are a few reasons large attachments have made things painful recently:
1. More and more people are sending >10MB attachments 2. The size of my local email archive is getting to be quite large 3. I reached my ~7GB storage limit on Gmail
I periodically mitigate the problem of a large local archive on my Mac by selecting offending messages (sorted by size) and using the menu option **Message->Remove Attachments** in Mail.app. I've mapped a keyboard shortcut to this menu option because I use it so frequently.
before and after removing attachments
On a Windows machine running Outlook, you can edit a message, delete the attachment, and then save the message. It takes more steps, but it's possible.
The Gmail issue is harder to deal with. Gmail doesn't have a sort by size option, so you have to use IMAP to suck down your mail before you can sort by size -- not a good option with a 7GB archive. Also, you can't edit emails in Gmail to remove attachments; you have to either delete the message or archive it. I solved this problem by paying $5/year for 20 extra gigabytes of Gmail storage. Cheap!
I've recently been toying with the idea of using Gmail as my primary mail server (previously, it has only been acting as a secondary mail archive / aggregator, which has the added benefit of allowing me to search my mail from a mobile device). I wondered, however, what would happen if I were to remove an attachment from a message in IMAP and then save the message...? Would Gmail allow message editing?
The answer is no. The message gets duplicated in Gmail.
I suppose I could then go in and delete the large message(s) from Gmail's archives, but that seems like it's too much work. In 2 years, I'll pay another $5 for 100GB of storage (or whatever). :)