Is there a time limit set somewhere that a message will be removed from the queue after retrying for a certain period of time? Or doing messages have to be manually deleted if they never go through?

Exchange 2007 Configure Message Expiration settings on transport server Configuring Transport Server Properties Exchange 2003 Admin Group -> Servers -> <server name> -> Protocols -> SMTP -> Default SMTP Virtual Server -> Properties -> Delivery Tab -> Expiration Timeout

Thank you very much for your response. This looks to be exactly what I am looking for. Unfortunately, the messages are not being removed after the expiration timeout (currently 2 days). We have messages at the moment from the 14th of this month. We don't want to have to manually clear messages out of the queue. Any thoughts?

In which queue mails are getting stuck? What is the Time submitted and Time expiration of those messages showing in queue?

Four different queues, lycosmail.co.uk, globalacross.com, myfirstmail.com, and barbarajordan.com. The messages within these queues are all being sent by the postmaster. The times submitted are yesterday and expires tomorrow. But when you look at the view of all queues, the "time oldest message submitted" is from the 14th, 18th, and 20th for the different queues. I guess it's no big deal, I can just delete these few as I see most other queues are following the two day rule.

Amit, mentioned good point. I'm not too good in mail transfer issues. But, I did some testings earlier and it worked for me. They might spam recipients which are not part of their domains. On the outbound Exchange SMTP Servers, you can try adding these domains "Recipient Filtering" Open ESM | <Org Name> | Expand Global Settings | properties of Message Delivery | Recipient Filtering tab Add recipient as *@lycosmail.co.u, I think Exchange understands * as recipient alias of remote domain.