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UBC Mathematics: MathNet FAQ [Lost Email]

UBC Mathematics: MathNet FAQ [Lost Email]

Question: My Email didn't arrive or I didn't get Email? Where did it go?
Author: Joseph Tam
Date: Jan. 15, 2007


There are many reasons that would prevent an Email from getting to its destination (whether that be your mailbox or someone else's). Here are some common reasons:

  1. Wrong Email address: either the username portion or the domain portion may be wrong. A common mistake is to include specific hostname to an Email address, such as "user@host.mail.domain" when the correct Email address is "user@mail.domain". You ought to get a notice of this ("bounce message").

  2. Mail too large: most places have restrictions on the size of a single piece of Email they will accept. Exceeding that limit will result in the mail being rejected. You ought to get a notification when this happens.

  3. Mailbox is full: our site enforce storage quotas. If your mailbox size exceeds your allotted limit, no Email can be delivered until you make more space available (i.e. delete some Email). See elsewhere in our FAQ to see how to check quotas.
  4. Mail server is busy or not operational: a mail server (either sending or receiving) may not always be available to immediately deliver mail. In these cases, mail will be queued and delivery retried at periodic intervals until the receiving mail server is available. If the mail server does not respond in a reasonable amount of time, the mail will be deemed non-deliverable, and a bounce message will be sent back to the sender.

    The retry interval and the total retry time policy is set by the sending Email server: at our site, mail will be retried every 4 hours for a maximum of 24 hours.

  5. Blacklisting or spam/virus filtering: some sites use blacklisting, or spam or virus filtering to try to detect unwanted mail and reject them. Depending on the mail policy at the offending site, the sender may or may not be given notice that mail has been filtered.

    At our site, we do employ blacklists and do virus filtering. The sender always gets a notice stating the reasons why their Email was rejected, but some Email users are not techically savvy enough to understand what's going on. If you suspect that Email being sent to you is being blocked, contact the IT staff (see below about reporting mail problems) and they may be able to suggests workarounds or remedial actions.

  6. Mail being forwarded incorrectly or mail loops being formed.

  7. The user has set lax permissions on their home directory. Our mail server, for example, will refuse to deliver mail to a user with a home directory that is world writable.

Most of these problems are apparent when an error message occurs (either from your mail reader or from a Email rejection notice).

How to report problems

When reporting mail problems, it is important to give as much detailed and accurate information as possible. Sometimes the only way to diagnose these problems (especially when the problem is days or weeks old) is by looking through the mail logs, and precise time/sender/recipient details are required to track the problem down. Email headers (envelope information) from Email (if available) is usually useful, and should also be included when reporting problems.