Bounce Email Messages

Bounce e-mail is electronic mail that is returned to the sender because it cannot be delivered for some reasons. Bounce e-mail usually appears as a new note in your inbox. Ideally, these bounces take the form of SMTP codes. Using these codes, ISPs (Internet Service Providers) can communicate the reason for the bounce. Not everyone follows this standard however, and accurate bounce handling may involve some keyword review of the replies.

Typically, a bounce message will contain several pieces of information to help the original sender in understanding the reason his message was not delivered:

    * The date and time the message was bounced,
    * The identity of the mail server that bounced it.
    * The reason that it was bounced.
    * The headers of the bounced message.
    * Some or all of the content of the bounced message.

 E-mail users can encounter bounce e-mail because an addressee has changed his or her address, because their mail box is full, because the note is misaddressed, or for some other reason. Regardless of the bounce message’s, there are two types of bounces: soft and hard.

A soft bounce is an email message that gets as far as the recipient’s mail server (it recognizes the address) but is bounced back undelivered before it gets to the intended recipient. A soft bounce might occur because the recipient’s mailbox is full, the server is down or swamped with messages, the message is too large or the user has abandoned the mailbox. Most email service providers will attempt to deliver the email regularly for a few days. If it is still undelivered, it becomes a hard bounce.

A hard bounce is an email message that has been returned to the sender and is permanently undeliverable. Causes include invalid addresses (domain name doesn’t exist, typos, changed address, etc.) or the email recipient’s mail server has blocked your server. Servers will also interpret bounces differently, meaning a soft bounce on one server may be classified as a hard bounce on another.

Common Error Messages

    * Mailbox unavailable - 9 times out of 10, this is the same as “mailbox not found. It could mean that there’s a problem with the recipients email account.  Make sure that you have the email address correct, wait a while and try again, and if it still bounces, try contacting the recipient some other way.
    * Host unknown, Domain Lookup Failed- this means that the mail server you’re trying to use doesn’t exist. Make sure if you typed it in correctly. Another reason are ISPs that change their name.
    * Mailbox full- sometimes this can be shown as ”mailbox unavailable” message. Your recipient has too much email and their server isn’t accepting any more. This can also be a sign of an abandoned account - someone’s stopped looking at and cleaning out the email. In any case, you’ll need to contact your recipient in some days or in some other way.
    * Unable to Relay - this is a vague error message, but also becoming more and more common as ISPs try to crack down on spam.
    * Temporary Errors - there are errors like “Resources temporarily unavailable.”, “Connection Timed Out”, “Out of memory” all of these indicate a problem with a mail server that in general is temporary, and should resolve themselves over time.
    * Content Filters -  Phrases in the bounce message like “Message looks like spam”, “keywords rejected by the antispam content filter”,  and similar means that your email, for whatever reason, tripped the spam filters on the receiving end.
    * Blacklist Filters- If you receive messages that indicate that your email was “blocked”, or “listed in”, then your email was probably intentionally blocked because the receiving system thinks your ISP’s mail server is a source of spam.

Monitoring bounces can help you to find a potential delivery problem and after every campaign, you can quickly correct any irregularities. Here are some tips to help effectively deal with or minimize email bounces:

    * ISP?s recommend retrying hard bounces no more than three times. In our experience, retrying a hard bounce only once after a period of two to four days is sufficient.
    * To ensure subscribers enter their e-mail addresses correctly, include a script that checks for syntax errors upon submission.
    * Use an e-mail change of address service to help combat e-mail address shaking in your mailing list.
    * Use a double or confirmed opt-in subscription process to minimize incorrect and false addresses from the beginning.
    * Monitor bounce rates , and establish a benchmark. Analyze the cause, and take appropriate action when a message lies outside of the norm. Add an e-mail address update link to your e-mail and a profile update form to your Web site, enabling subscribers to update their address and preferences.
    * Remove hard-bounced addresses from the list immediately or after the retry attempt fails. Remove soft-bounced addresses from the list if the address repeatedly generates bounces over a period of four to five e-mail campaigns.
    * Consider contacting bounced subscribers via postal mail or phone to obtain their new e-mail addresses.
    * Scan keywords when processing bounces to help deal with non-standard bounce messages.
    * Monitor bounce messages for signs of e-mail rejection. The message may have been rejected due to blocking or filtering and you may need to contact the administrator of the receiving system.
    * Pre-test messages for potential spam-oriented content to help minimize rejections by ISP and corporate spam filters.