Yes, they are on AD and I there is a group policy.

For what should I look in that policy?

No unusual, just this one that I was expecting

Logon Failure:

  Reason: The user has not been granted the requested

   logon type at this machine

  User Name: 

Domain:  [domain]

  Logon Type: 5

  Logon Process: SCMgr  

  Authentication Package: MICROSOFT_AUTHENTICATION_PACKAGE_V1_0

  Workstation Name: [workstation]

If I put the same user with the same password in EM will work again for a period of time.

On the server I have enabled auditing for success and failure...

Amen

I have encountered this issue or a similar on, the way a solve it was to put a space between recipients after the semicolon.

You can try to restore the transaction log then move it to another folder that will assure that you will always have only one file on that folder/backup device.

correction

RESTORE LOG [database]

FROM [dump device]

WITH STANDBY [standby file]

For a custom log shipping I am using

RESTORE LOG [database]

FROM [dump device]

WITH STANDBY

is working fine for me.

I am not sure if you need to reboot but I am doing it all the time.

Check the paging of the server you might have just an I/O bottleneck.

You can try also the xp_smtp_sendmail

I think the issue was fixed on SP3a

Acording to Lise Cheron this will do the trick

"Yes I changed the SQL Server Agent startup account (you can overwrite your exisitng one) from ets manager. In this way all...

You can use the dtsrunui.exe application usually under C:\Program Files\Microsoft SQL Server\80\Tools\Binn to generate the correct syntax. 1. Advance 2. Generate.

This is what I got for a transfer from pubs...

I am using xpsmptd.dll, works great. The only observation is that after 1000 chars in the message is inserting a space so if you intend to send HTML formated messages...