We have had issues those last days with the maptools.org server hosting this
mailing list being blocked from sending emails, due to spam transiting through
it. This has been unblocked for now, but it might happen again.
We have requested migration of this mailing list on the lists.osgeo.org
infrastructure which has more knowledgeable people already handling a very
large number of lists.
We'll try to migrate as much as possible, including the existing subscriber
list, but in case this would not be possible, you might have to subscribe
manually to the new list. We'll try to inform you of what happens on this
channel, but if communication here doesn't seem functional anymore, please
refer to the above link where instructions we'll be given.