Yes, I manage an Axway (formerly Tumbleweed) Secure Messenger server. Been using it for about 4 years now and it works very well. Support was excellent prior to the merger of Tumbleweed and Axway, but I can't really offer any opinion on support through Axway because I haven't had a need for support in the 2 years or so after the merger.
I've never heard of smarsh or electricmail. I remember looking at Zix when we were looking to buy, and their product was very similar to Tumbleweed. It has some value-add if you had a lot of business parters that also use Zix because it could negotiate a secure transfer between the two Zix servers instead of sending the recipient a link to retrieve the email by logging into an SSL web-mail client.
Do you have a set of requirements for your implementation? How many users? What is your existing email infrastructure?