How can I use my host's SMTP to send mail when I have my address set to forward incoming mail?

You correctly identified you need to use your host's smtp server to send mail if you want it to look right. I would guess the error is because there is a problem connecting on port 25, rather than something about mailboxes. I don't use 1and1 but some ISPs don't allow connections from external networks on port 25 to cut down on spam. Does 1and1 have a support forum etc? if you want to check the network connectivity, telnet to smtp.1and1.com on port 25, it will display exactly what your mail client sees when it connects (or fails to).

You can use Google Apps for your Domain to set up some similar magic; I think you can still send mail from an account that is otherwise forwarding mail. I'm sorry I don't have the time to go through the entire process right now to confirm, though.

If you can't connect to port 25, it's probably your ISP. Does 1and1 allow SMTP to port 465 or 587? Those are the typical alternative TCP ports for mail handling. Note that 465 is the default SSL port, and you'll need to turn on SSL to use that. Note that we haven't gotten to the point where we find out if your account at 1and1 allows SMTP relaying, rather than the forwarding you've described. We have to first solve the basic connectivity issue with the SMTP server.

Try setting your phone and mail client to use port 587. That's the SMTP submission port, and it's designed for users that have accounts on the remote SMTP server to do just what you want (relay). On iPhone, change your outbound mail server to smtp.1and1.com:587 .. on your client, just change the port to 587. Leave all authentication settings in place and I bet it works. (This is what I do to relay through the mail server I operate, because virtually all Internet providers block port 25 outbound to "random" servers)

These are much quicker replies than I expected. This is all extremely informative, thank you! I just sent a test email, and I'm able to send email from other accounts, such as Gmail's SMTP server and my work's SMTP server, on port 25, with my ISP (which is comcast). I've tried setting smtp.1and1.com to specify port 465, and then 587, and neither yielded different results. Out of suspicion, I logged into my host's site (1and1.com) and changed [email protected] to a normal 'mailbox', instead of a 'forwarder.' Then I set up Mail.app to check this mailbox. Once I did this, I was able to send outgoing emails using my host's SMTP server. These emails had the correct [email protected] return address. But once I changed [email protected] back to being a 'forwarder' address (not a "mailbox") on my host's site, I could no longer send emails from that same SMTP server. Instead, I receive the dialog, "The SMTP server smtp.1and1.com rejected the password for user [email protected]. Please re-enter your password, or cancel." This dialog would not accept the password that previously worked.

PS if it's still of any use, I can telnet to the SMTP server on port 25 (as bystander asked). The result is: $ telnet smtp.1and1.com 25 Trying 74.208.5.2... Connected to smtp.1and1.com. Escape character is '^]'. 220 smtp.perfora.net (mrus1) Welcome to Nemesis ESMTP server and then of course eventually 421 smtp.perfora.net connection timed out Connection closed by foreign host.

In Mail.app http://it.seas.harvard.edu/operations/support/services/email/configure-email/files/mail.app/account-prefs.png, for your email account, in the "Email Address" field, add your other account name. So that it reads "[email protected], [email protected]" (I assume that this is possible with a me.com account. It works for pop/imap accounts.) There ma, however, be some indications that the mail is delivered through me.com. Looking cloesely at the headers, your mail is coming from Apple's me.com SMTP server. But the 'from:' line in your email messages should show the @my-domain.com address.

Actually, in Gmail settings, once you've added a pop account to your gmail account, you can tell it to NOT grab mail from it. In the settings screen there's a "send mail as" option, where you can select the other email address as an option. Then in the compose screen, you just select which FROM email address you want to use.

I have a similar set up, and what I've done is to have a "real" account *and* a forwarder for the same account. I then have a mail.app filter which automatically tosses any mail it receives on non-me.com accounts. I don't know if this is something that your 1and1 account will allow you, but my service provider does, so I guess you're chances are reasonable. I've been using this set-up quite happily for a few weeks now.