Unlike the Option 11, wjere you can do an AX to get to Mermail and a CTRL-] tp get back to the PBX, you cannot do this with the Opt61/Meridian Mail.
There are a couple of options for you. Use a Terminal Server type device where you can put both the PBX and Mail on it, then telnet in to the TS and connect to either port. OR if you have a spare MSDL card, you can setup an application called Single Terminal Access. Basically, you hook up the PBX, Mail and two other devices of your choice to the MSDL. When accessing, your given a menu for device selection. See the System Managment and Applications NTP for info on STA. It works, but can sometimes be a pain. The MSDL will occasionaly lose its head and you have to disable and redownload the card.
I use ION Networks Secure Sentinels alot. The Slimelines
have 4 RS232 Ports, 2 modems and a 10BaseT connection. The device provides multiple security options, user ids, etc..
You can dialup from home, and telnet in when you are at work. Also, when dialed up from home, you can jump between ports without having to hangup and redial.