Postie stopped working via Non-SSL POP3

I had Postie set up to process emails via regular POP3 (not SSL) and it had been working fine for a while. Then all of a sudden, it just stopped working. I had not changed any settings on the server or on Postie, but it just would not process emails anymore. When I enabled debugging, this is what I got:

Postie: Checking for mail manually
Postie: Starting mail fetch
Postie: Time: 2013-03-11 12:37:14 GMT
Postie: wp_content_path: /home/public_html/wp-content
Postie: Connecting to mail.mydomain.com:110 (pop3))
Postie: pop3 cannot delete message POP3 delete: Command failed []
POP3 reset: ERROR [Thu, 07 Mar 2013 08:06:12 -0500]

So this message came from Postie after trying to delete a message it retrieved for processing:

pop3 cannot delete message POP3 delete: Command failed []

And this message came from the WordPress POP3 class after trying to send a RSET command.

POP3 reset: ERROR [Thu, 07 Mar 2013 08:06:12 -0500]

When I changed Postie Option “Delete email after posting” from Yes to No, then several (but not all) posts were published. However, I received a string of identical error messages like this:

Warning: implode() [function.implode]: Invalid arguments passed in /public_html/wp-content/plugins/postie/postie-functions.php on line 714

The “implode” error indicates that there is something going on with my email server, but I am able to access it via webmail and I can pop the account via Gmail (POP3-SSL).

I changed Postie settings to connect to my mail server via POP3-SSL and presto! I’m back in business.

The solution to this problem for me was to switch from Non-SSL POP3 to POP3-SSL.

http://wordpress.org/extend/plugins/postie/