I am trying to figure out what is the best way forward when applying Mainteannce Releases etc.

We are running BES 5.0.3 build 33, so I need to install Maintenance release 1 through to 7.

Our configuration is we are using HA (so have Active/ Passive nodes) and have SQL Mirroring in place.

For Example, I am guessing I apply MR1 & 2 to the passive BES node and then on the Active one (after reading other posts). These 2 do not touch the db. But when applying MR 3, the db is updated, so do I need do anything on the SQL Mirror etc.

I am just trying to figure out the best way.

Apply only MR7, no need to apply the older ones as MR7 contains the old ones.

knotty is correct, the MRs are cumulative.

With a HA config, do the following:

1. Backup the BES SQL DB
2. Upgrade the Standby Instance to MR7 (this will upgrade the DB)
3. Fail over
4. Upgrade the new Standby instance to MR7
5. Fail back (optional)
6. Upgrade the BES remote components such as BES Router, BES Attachment Service etc.

I take it that also means that I dont need to failover SQL to the Mirrored Server and upgrade it as well, as the DB changes will mirror across to the mirrrored Server when its upgraded by the Passive Instance upgrade step.

That's correct. Database mirroring replicates DB schema changes, so no extra step there.