I did set up an SQL Agent Proxy account, logged it on the server (in a
Remote Desktop), and created various Outlook Profile to be used from
within DTS Packages. They all are copies of one initial profile to
cover the various profile names found on clients ("Outlook", "MS
Exchange Settings", ....)

DTS Packages were able to send mail even when started within Jobs with
non-SysAdmin owners - regardless whether I started the Jobs scheduled,
manually in Enterprise Manager on the server or a remote client.

So far, so good.

Then I closed the Remote Desktop and suddenly the SendMail Tasks did
not work anymore.
The error is "80040480 MAPI error : MAPI Logon failed" or so without a
number - it is *not* the infamous MAPI error 273 caused by different
profile names on clients and server.

I found out that when I open another Remote Desktop - and even when I
disconnect it directly after logging in (but keeping the session on the
server) - DTSMail starts to work again without any modifications....
The moment I (for example) reset the connection and therefore close the
session from the Terminal Services Manager of another server, DTSMail
fails again.

This is reproducible.

I checked the User Rights Policies and the Proxy Account has "Log on as
a batch job" as documented.
In addition I gave it "Log on locally" and even "Log on as a service",
but neither helps.

???????????????????????

Nobody ??!!!

In the meantime I found another "workaround" : if I am logged on as
Administrator and do a "runas /user:ProxyUser cmd.exe" DTSMail works as long
as that Command Prompt is open....