"@" character not accepted by login and password prompt

[doug mielke]

The different behaviours at different times / locations could be explained by TERM.
Since this problem happens at login, you would be using a different TERM setting than after they log in to change passwd (listed in the system or users profile), since at this point, that hasn't been read.

[Bill Hassell]

Be careful about mixed platforms. No one at Microsoft consults with Unix vendors to see what would be compatible (and vice versa). There will always be differences (especially for user names and passwords) that cannot be made compatible across all platforms and special characters are the most common class of incompatibilities. While the ttyconf solution handles (current patches) HP-UX, there are no guarentees that a special character will not cause problems with other systems. Alpha-numeric is 100% safe and creative passwords like v6dGys32 are excellent but just a bit difficult to remember. Another alternative is to use the first letters of a sentence or motto.