I found this solution in the Palm, Inc. support library:
http://kb.palm.com/SRVS/CGI-BIN/WEBCGI.EXE?New,kb=PalmSupportKB,CASE=obj(2325),ts=Palm_External2001
Solution ID: 2325
'354 Enter Mail, end with '.' on a line by itself.' (when sending email with VersaMail)
This error can appear when you try to send an email with VersaMail. It happens because of a semicolon (

at the end of the list of email recipients.
Why does it happen?
The VersaMail application automatically puts a semicolon at the end of every email address when you use its Auto-Populate feature. This makes it easy to input multiple email addresses using Auto-Populate, without needing to manually add semicolons between each address.
For example, your To, Cc or Bcc line might look like this:
[email protected];
[email protected];
[email protected];
Note the semicolon inserted at the end of the last email address.
A few email servers get confused by the final semicolon; they think it indicates there should be another email address after it. When this happens, you'll see the error 354 Enter Mail, end with '.' on a line by itself.
What to do
If you encounter this error, it means you are one of those few whose email server has a problem with the final semicolon.
When sending an email, make it a habit to remove the final semicolon from the list of recipients (To, Cc, Bcc).
Heather