Email Address Errors

If an addressing error arises when sending email, you will usually get a bounce email returned to you with an error message. Possible solutions are described below.

  • Spelling Error. The most common error is a mistyped address, which usually produces a “no such user” error message. Double-check the address, and if necessary phone the recipient and ask them to send you an email so you can cut and paste their address into your address book to guarantee it is entered without error.
  • Under / over-specification. Occasionally you find an address is under or over-specified. For example, you may receive an email from a third-level domain name like “”, but their system is set up to only receive email addressed to the second-level name “”, in which case you can change the address and try again. Similarly, if the email is labeled “” and you are sending to “”, then try sending to the full third level domain name.
  • Wrong Reply-To Field. A not uncommon error is to configure a different address in your “Reply-To” field from the “From” field, usually by a spelling mistake. The Reply-To field is used by some email programs when the Reply address is different than the From address, for example when email is from a list server and replies should go to the mailing list address. However, for most people the Reply-To and From addresses should be the same, and if the Reply-To field is different it can cause problems.

    Check your bounced email to see if you sent it to the same address it was received from. If you replied to their email with the Reply function, it might have been sent to the Reply-To field instead of the From field — check if that address is different. If this is the cause, then reply to the email again, but manually copy the correct address from the From field, and let the recipient know that they need to correct their Reply-To address.

Historical. The following suggestions apply mainly to older systems, and should rarely be needed on modern system today, but are included for completeness and historical interest:

  • Bang Addresses. If the address uses the old “bang” format of specifying a path with exclamation points, then the exclamation points might be mistakenly interpreted as shell script commands and interfere with your message transmission, as in the following example:


Putting slashes “” in front of each exclamation point will sometimes tell the destination computer that they are just separators and not instructions.


  • Bitnet. To send email to a user on Bitnet, you sometimes get an address that doesn’t have a domain name specified, and you have to append the name “.bitnet”.



If that doesn’t work, change the at sign to a percent sign, and send it to a Bitnet gateway:

  • Compuserve. Old Compuserve addresses are made up of two numbers separated by a comma and no spaces, followed by “”


Sometimes the comma causes problems. You can try changing it to a period.

  • FidoNet. Fidonet addresses are made of a user name and a system node number. System node numbers are made up of a zone, network, and FidoNode number




1 for the U.S. and Canada, 2 for Europe and Israel, 3 for Pacific Asia, and 4 for South America


The network number in that zone


The BBS number on the network

Format: zone:network/FidoNode

Example: 1:287/156

You can construct an Internet address from a FidoNet address by prefixing the zone with a “z”, the network with an “n”, the FidoNode with an “f”, reversing their order, appending “”, and prefixing with “firstname.lastname@”.


To send to an Internet address a FidoNet user sends an email to UUCP, enters the node number of a UUCP gateway in the node-number field, and puts the Internet address as the first line of the message.

Node-number: 167
Hey John, hope you’re having fun ….