In order to be able to access Software Updates via the official Sun server, you need to register your system using a valid account. You can use the sconadm command to do so. Note that this one is the command line version of the /usr/bin/updatemanager program.

First, prepare a registration profile, enabling authenticated web proxy support:

# cat /tmp/registrationprofile.properties
userName=aaaaaaaa
password=bbbbbbbb
hostName=cccccccc
subscriptionKey=
portalEnabled=false
proxyHostName=dd.ee.ff.gg
proxyPort=hhhh
proxyUserName=iiiiiiii
proxyPassword=jjjjjjjj

Then, be sure to have correct permissions and mode on the profile (especially since passwords are stored in clear text). Last register the system:

# chown root:root /tmp/registrationprofile.properties && \
  chmod 400 /tmp/registrationprofile.properties
#
# sconadm register -a -r /tmp/registrationprofile.properties
sconadm is running
Authenticating user ...
finish registration!
#
# rm /tmp/registrationprofile.properties

You can now configure the sconadm CLI utility to use the authenticated web proxy configuration permanently, as follow:

# smpatch get
patchpro.backout.directory      -       ""
patchpro.baseline.directory     -       /var/sadm/spool
patchpro.download.directory     -       /var/sadm/spool
patchpro.install.types          -       rebootafter:reconfigafter:standard
patchpro.patch.source           -       https://getupdates1.sun.com/
patchpro.patchset               -       current
patchpro.proxy.host             -       ""
patchpro.proxy.passwd           ****    ****
patchpro.proxy.port             -       8080
patchpro.proxy.user             -       ""
#
# smpatch set patchpro.proxy.host=dd.ee.ff.gg
# smpatch set patchpro.proxy.port=hhhh
# smpatch set patchpro.proxy.user=iiiiiiii
# smpatch set patchpro.proxy.passwd=jjjjjjjj
#
# smpatch get
patchpro.backout.directory      -               ""
patchpro.baseline.directory     -               /var/sadm/spool
patchpro.download.directory     -               /var/sadm/spool
patchpro.install.types          -               rebootafter:reconfigafter:standard
patchpro.patch.source           -               https://getupdates1.sun.com/
patchpro.patchset               -               current
patchpro.proxy.host             dd.ee.ff.gg     ""
patchpro.proxy.passwd           ****            ****
patchpro.proxy.port             hhhh            8080
patchpro.proxy.user             iiiiiiii        ""

So you can now easily analyze your system and see what patches are published online and ready to be applied:

# smpatch analyze
[...]
118855-36 SunOS 5.10_x86: kernel patch
119999-02 SunOS 5.10_x86: arp, ip, ipsecah drivers patch
124923-02 SunOS 5.10_x86: ld.so.1 patch
122033-03 SunOS 5.10_x86: Update timezones patch
125012-01 SunOS 5.10_x86: sendmail patch

At this time, you can choose to download and apply them all. I some updates required a (clean) reboot to be effective, smpatch will tell you how to do properly:

# smpatch update
Update 122033-03 will not be downloaded since it already exists in the download
 directory.
Update 124207-02 will not be downloaded since it already exists in the download
 directory.
118844-30 has been validated.
118855-36 has been validated.
119999-02 has been validated.
124923-02 has been validated.
125012-01 has been validated.
Installing patches from /var/sadm/spool...
NOTICE: Update 118844-30 cannot be applied at this time since it is typed as
 "single user, reconfig immediate" which is disallowed by installation policy.
NOTICE: Patch 118844-30 cannot be installed until the next system shutdown.
NOTICE: Update 122033-03 cannot be applied at this time since it is typed as
 "single user" which is disallowed by installation policy.
NOTICE: Patch 122033-03 cannot be installed until the next system shutdown.
NOTICE: Update 124207-02 cannot be applied at this time since it is typed as
 "single user, reconfig immediate" which is disallowed by installation policy.
NOTICE: Patch 124207-02 cannot be installed until the next system shutdown.
/var/sadm/spool/patchpro_dnld_2007.01.31@13:10:10:CET.txt has been moved to
/var/sadm/spool/patchproSequester/patchpro_dnld_2007.01.31@13:10:10:CET.txt

ID's of the updates that are disallowed by installation policy have been
written to file
        /var/sadm/spool/disallowed_patch_list

One or more updates that you installed requires a system shutdown to activate
 it. To initiate the system shutdown, you must use one of the following
 commands:
o Drop to the firmware prompt - init 0 or shutdown -i 0
o Power down the system - init 5 or shutdown -i 5
o Restart the system - init 6 or shutdown -i 6

The bad thing is that this tool doesn't always as expected... particularly on older releases. Please refer to Matty's entries on this subject for more information.