For some reason I am having trouble getting specs on the Express VM module. I need an 8 port card but how many message boxes and how many minutes/hours of storage do they come with? I have downloaded the PDFs from Mitel and I can't see this listed

Are there other VM systems that will integrate with an SX-200 digital system?

I am new to Mitel.

Basic system with 131 hours of record time and not sure on the maximum number of boxes but since it is designed for Mitel SX200 should be in excess of 500. Only works with LW17 and above. You say you have an SX-200 Digital which would not work.
Many other systems will integrate with the Mitel PBXs using analog, digital, or COV integrations.

If you have rev 4.11, you can have 300 TOTAL mailboxes.
Lower revs had a max of 250 mailboxes.
As mentioned, the Express Messenger will not work on the 200D systems, you'll need an ML/EL running LW 17 or better.
I know a great company that can supply everything you'll need!!

I did a site visit today. I confirmed one building has a MCIII-ML Stratum 4 with an LW19 card. The other building has a MCIII-ELx Stratum 3 - unable to confirm card because I could not power down the switch and pull the card.

These two buildings have 4 digit extension transfer via station to station dialing. I need to add a voicemail card to this. The Stratus 4 looks good to go. Now if I add the card in that unit, can the other building use the VM too or do I need a card for both switches?

If I need to upgrade the Stratum 3 to an LW19 what is involved?

Pardon my novice questions but I've never workled on a Mitel before.

All's you need on an upgrade to LW19, is a flash card, and a system reset. Upgrading your feature level would be a whole different situation. Are the 2 Mitel's networked togeher, or is the 4 digit dialing actually going out on converted ars strings?
The single voicemail is possible, but will work a lot better if there are some sort of tie lines available.

To help you answer Fifty5footer's question: In form 26, is there a number that is the first digit of the extensions on the other PBX?

(i.e. Building 1 has extensions 4xxx, and there's a 9 and a 5 in form 26; Building 2 has extensions 5xxx, and there's a 9 and a 4 in form 26). Obviously the 4 or the 5, if you highlight it and "Show Strings" would just have routes that point to the other PBX.

If so, then those are "tie lines."

I'm not sure that it won't run in a 200D. I think I put one in a Light running LW16 on the bench and it did function. The extra options mat not work, but basic functionality seems possible.