[exim] problem with authentication and virtual users

Hi,

I have a virtual user setup with exim + teapop and on the intranet side
everything is working fine. Problems start when trying to authenticate
from the outside. I've tried ssl, tls, no encryption... I have been able
to get deliveries through, but only after waiting about 45 sec. (and
sometimes timing-out a couple of times). Authentication is been done
against a mysql table.

I've tried to telnet from the outside, but I don't even get a response
from port 25 with telnet. From the inside telnet works ok without
encryption.

I've been googling for two days and changing all sorts of config
options, but I'm not able to get anywhere. Someone knows where my config
may be failing? May there be some interference from another package?

All other aspects work flawlessly: virtual re-directs, virtual users,
local delivery, etc.

Thanks. Any help will be welcome
Robert.

PS- I'll post logs if needed. Just tell me which ones would help.