If apparently valid subscriptions are not processed there may be different reasons:

1. The e-mail address they are sent to is not the address used for managing the list
2. The originating address is already present in the list
3. The wrong list was selected (please remember that each list has a different account)
4. The subscribe message has a wrong format
5. The message was already processed before
6. The new messages are not subscriptions, but “normal” messages on that mailbox (they could even be spam)

To test that everything is ok, you should create a blank “test” list, configure a fresh e-mail address for managing subscriptions (please note that each list may have a dfferent account), send a subscribe message to that address, and then download subscriptions for “test” list. Bulk emailing can be easy with a bulk emailing software.