How can I automatically forward an e-mail and change sender?

I use E4ward for that purpose. E4ward allocates aliases, which look like [email protected]. I give out these aliases, and E4ward forwards emails sent to them to my real email address, but with a tricked return address that I can use to respond such that my answer would seem to come from the alias.

The advantage in that kind of service is that I'm less exposed to spam, and when I do receive an unsolicited email I know exactly who is to blame.

I have tried a dozen such services before settling on E4ward as the best. I used a free account for a couple of months, and was so satisfied that I paid the $10 yearly subscription. Their service is very complete, missing only the feature of auto-expiring aliases, which I don't need.

Read this article for a description E4ward.com - Disposable Email Address Service:

E4ward.com is a down-to-earth and very useful disposable email service that makes it easy to prevent spam to your real email address with easily erasable aliases. You can use your own domain with E4ward.com, but auto-expiring aliases are not offered.

• E4ward.com lets you set up unlimited disposable email addresses.
• You can set up custom aliases or use random characters to make guessing more difficult.
• Each E4ward.com can have a memo to help you remember which site or use
  it was set up for.
• E4ward.com lets you create aliases for multiple real email addresses.
• You can use aliases at your own domain name with E4ward.com.
• E4ward.com protects your real address even in replies by routing them through its servers.

I think you need to use something like procmail for this. I doubt you can do it with any free webmail client.

I think you have a few options:

1. Sign on with a web hosting company which gives you SSH access and the ability to tweak your own mail settings. Then set up procmail to do this. My host does this for $10/month.

2. Use a local mail client to do this. At the moment I have a rule set up in my University Mail program (a Web version of Outlook, connected to their Exchange server) to do just what you're asking. (In fact I wish I could do real forwarding where it looks like the email actually came from its original recipient, but that client won't allow it.) If you do this, all the email will be downloaded and then resent.

3. Talk to an email forwarding service (like pobox.com), explain your case, and see what they can do for you. It's a pretty simple request, which they may not offer as a stock option simply because most people want their forwarded mail to show the original sender.