A mailbox was migrated from Exchange 2003 to 2007. The mailbox limits (4.0gb, 4.2gb, 4,4gb) were kept as they we're over default size. The user cannot send mails though the size is under the limit (~3.7gb). I've tried to set even higher limits with no succes (did wait for at least 2 hours).
What could be wrong?
Maybe you're hitting different type of limit then mailbox size: http://www.msexchange.org/articles-tutorials/exchange-server-2007/management-administration/exchange-2007-message-size-limits.html
Please check the tutorial to set/check other limits and see if that might be the case. Also having an error from the mail that returned would be great.
What do your log files and error messages say? Are you sure it's a mailbox limit issue? Check EMS to confirm the storage quotas ( http://msexchangeteam.com/archive/2006/09/20/428965.aspx ).
Also see: Mailbox Size Limits Are Not Enforced in a Reasonable Period of Time http://technet.microsoft.com/en-us/library/bb684892%28EXCHG.80%29.aspx