Filters run automatically only on the Inbox, and only affect Inbox messages. To apply them to other folders such as Sent, they must be initiated manually, as you describe.

So why include a "To" option because all emails that I send "To" someone all go to the Sent folder and there fore by your reasoning wouldn't be detected by the rule?

The To, Cc or Bcc options allow for a filter to be applied to a folder with sent messages. If such a filter is applied to the Inbox, only the From or Cc options are relevant.

Hmm the fact is that the messages from two of my contacts always get sent to the deleted folder despite there being filters to move them to their respective folders. The ones I send to them are picked up by the rule and moved correctly. I've checked and rechecked and none of my rules send anything to deleted??

Check the account in webmail in case the mail provider is filtering those senders, e.g. marking as spam and deleting. It might help to whitelist those contacts by adding them to webmail contacts.

Check the account in webmail in case the mail provider is filtering those senders, e.g. marking as spam and deleting. It might help to whitelist those contacts by adding them to webmail contacts.

Thank you and I had just tried that when I saw your reply. There wasn't anything that I could see affecting the contacts in webmail but I've certainly added them to my contacts (as indeed they were in T/Bird) So I'll just have to wait and see what happens when I get more from those two addresses. Thanks