Problem: I'm trying to send email, and I get back an error message such as "550 Relaying denied". What does this mean, and why can I not relay email through chemistry anymore?

If you use Eudora, Outlook Express, Netscape or any other POP or IMAP mail client to send and receive email, you have configured an SMTP server. For a computer in the Chemistry Department, the correct SMTP server is "chemistry.ohio-state.edu". The SMTP server is the machine through which your mail program sends outgoing email.

Whenever you send email from host A through the SMTP server chemistry.ohio-state.edu to host B, then you relay email through chemistry.

If your host A is a computer in the Chemistry Department or within the University (Homenet is within the University), relaying email through chemistry is a normal and intentional procedure; destination host B can be anywhere in the world. However, if your host A is a computer outside the Department or the University, then relaying becomes an issue.

In a happier and freer time, when the Internet was not about making money, it was generally accepted that mail servers would freely exchange mail. Any server would pass mail that it neither originated nor for which it was the final destination. In this way, the loosely connected networks of Universities and Government Agencies that made up the early Internet formed a cohesive whole as far as email was concerned. This worked well until the Internet turned commercial. ISPs started charging for email that passed through them or started restricting the number of messages their customers could send. Additionally, people found that they could make money using bulk email. Mail servers that remained open to relaying were more and more abused by bulk emailers and spammers. This led to the creation of black-lists of all mail servers on the Internet that (still) allowed relaying in an effort to reduce spamming, and people started to refuse email from those sites. In order to guarantee stable email connections to other hosts, we therefore could no longer allow relaying.

As long as the destination host B is within the University (i.e. as long as its address ends in ohio-state.edu or osu.edu), you can relay through chemistry. If both A and B are outside the University, relaying is denied by default. This policy has been in effect since December 1999.

There were two solutions for departmental users with computers at home or with laptops. Solution One was to use the SMTP server of one's ISP (Internet Service Provider) instead of chemistry.ohio-state.edu. For users with laptops, this meant that they had to switch to a different SMTP server when taking the laptop off campus. While the laptop was in the Department, the SMTP server was chemistry.ohio-state.edu; while the laptop was elsewhere, users had to put in the SMTP server of their ISP. Solution Two was to tunnel the SMTP connection through SSH (described in detail in the The GreatSSH Primer), but this was a bit more complicated.

We now have a mechanism in place that will allow relaying of email to users who authenticated with their username/password. Since spammers don't have chemistry accounts, they will continue to be denied relaying through our site. It can be configured by checking a few boxes in many email clients and does not rely on SSH software. With these settings and chemistry.ohio-state.edu as your SMTP server, your client will work anywhere in the world.

Most modern email clients support secure connections. Many also support authentication. In order to relay, you must turn on both. The following example is for Outlook Express:

• Under Tools -> Accounts, select "Mail" and your chemistry account and press the "Properties" button
• Under the "Advanced" tab, check "This server requires a secure connection" for Outgoing mail (you should already have checked the same button for Incoming mail, since you need a secure connection to read email from outside the Department). The default ports chosen, 25 for outgoing and 993 (IMAP) or 995 (POP) for incoming, will be fine.
• Under the "Servers" tab, check "My server requires authentication" under Outgoing Mail server.
• Select "OK" and close the Internet Accounts dialog box.

The setup for Outlook is slightly different:

• Under Tools -> E-Mail Accounts, the "View or change existing e-mail accounts" radio button should be selected
• Click Next
• Highlight your chemistry account, click "Change..."
• On the next dialog, click "More Settings..."
• On the dialog, select the Advanced tab, check "This server requires a secure connection" for Outgoing mail (you should already have checked the same button for Incoming mail, since you need a secure connection to read email from outside the Department). The default ports chosen, 25 for outgoing and 993 (IMAP) or 995 (POP) for incoming, will be fine.
• On the dialog, select "Outgoing Server" and check the "My outgoing server (SMTP) requires authentication". The "Use same settings as by incoming mail server" radio button should be selected.
• Select "OK".

Older versions of Netscape Messenger may not have authentication built in. Netscape 7 and Mozilla Mail are identical to set up and don't have a separate check box for authentication (if "secure connection" is turned on, they will automatically attempt to authenticate):

• Under Edit -> Mail & Newsgroups Account Settings, select "Outgoing Server (SMTP)"
• Check "Use Name and password" and enter your username in the field provided.
• Check "Use Secure Connection": "When Available" or "Always".
• The port above should be 25 or empty.
• Select "OK"

Eudora 5.2 has built in support for SSL, but according to our tests, authentication will not work correctly (due to a problem with protocol negotiation). If you use Eudora from outside the Department, you'll have to resort to solutions One or Two above to relay email through chemistry.

The web-based email interface TWIG as well as host-based email clients such as pine and elm do not have any limitations with regard to sending email. In order to use them, you had to login with your username/password.