Filter rules are not case-insensitive, meaning that the rules ignore capitalization.
Comparison fields include the following:
From. Use this to specify a name in the From: header of an email message.
To. Same as From, but looks for specified names in the To: header.
CC. Same as From, but looks in the Cc: header.
Subject. Looks in the message's Subject header.
Header Named. When this option is selected, an additional text input field appears before the comparison operator (the "is" or "contains" portion). This option allows you to specify any email header. You can specify not only the standard fields of To: or From: but also Date, Reply-To, or other custom fields that may be included in the message header. You could use this option to filter out email messages that have "malformed" headers, meaning they do not contain certain information that is normally considered standard for an email message. Sometimes spam, which is automatically generated, omits information such as the Sender or Reply-To fields. Use the second text field (the field immediately to the right of the comparison operator) to specify the header to test for.
Size. Use this to select email messages that are larger or smaller than a specified size. The size of the email includes any file attachments. You can use this to discard email messages that are too large.
Date. Use this option to specify email messages sent before or after a specified date.
Body. The options for Body are Contains/Does not contain, and this allows you to specify matching words in the body of the email. You cannot filter for words in file attachments.
Attachment. You can filter for email messages that have, or don't have, file attachments.
Address In. Tests for the presence of an address in your contacts. The next field allows you to specify which address.
Comparison operators include the following:
Contains/does not contain. Specifies that the subject line must contain the specified substring. For example, specifying Subject contains "Banana" would match "I'm going bananas".
Matches/does not match. Exact match, but with wildcards allowed. For example, specifying Subject matches "banana*" would match "bananas" or "banana-leaf casserole" but not "my banana-leaf casserole."
Keep in Inbox. Saves mail to Inbox. If none of the filter rules match an email message, this action takes place by default.
File into folder. Moves the mail to a specified folder.
Discard. Deletes the mail message without delivering it. The message is not in any of your folders, not even Trash.
Forward. Forwards mail to the address you specify
Mark. Select as Read or as Flagged.
Tag with. You can tag matching messages with a selected tag.
A filter rule can specify multiple actions. The combinations of actions are interpreted as follows:
Discard. If combined with other actions, discard is ignored and the other actions take place.
File into folder. Multiple "file into" actions results in multiple copies of the message being stored in different folders. If a specified folder does not exist, the message is saved to the Inbox.
Tag/Mark. These actions apply to the message returned from the nearest preceding action. In the case of multiple "File into" actions, this could result in some copies of the message stored without a tag, and others stored with a tag.
Keep in Inbox. Multiple "keep" actions can be specified, but only one copy of the message is saved to the Inbox.
Forward to address. Mail is forwarded to the address specified.