obriensl, your setup is OK and safe.
I should advice you NOT to do that, and not even the automatic replies.
This is one of the methods spammers use to determine if an address exists or not.
They mail to random addresses to domains.
If an NDR is generetated, you actually confirm your domain, that gives them a free ride to try other mailboxes. They all return an NDR, except the real ones. BINGO, they got you!
So, beware!
Make SURE you 'higher up' people are aware of that, and make them know through an email and ask for confirmation. Otherwise you risk to get blamed later for allowing spam and other attacks.
Some people want it all, and jsd already summed up a good reasoning. If they are out, they are out, If they want business to run during absence, they should either read their mail from somewhere else or have it forwarded, period.
If YOU are responsible for security (and SPAM and relaying fall under that), then you should keep it disabled.
Try to convince mamagement of the huge problems this can cause.
The 'nice to have' options do not validate those problems, under no circumstances.
Out of experirience, I have been in similar situations, the boss WANTS it, so be it, I have never given in except once, and that was the only one preparing to sign a release to me not holding me responsible for future problems. I left there a while ago already, but my contacts there confirm the have now huge problems with spam.
Also point out that if you have to fix that later, it will cost them dearly on Anti_spam software, for something that can easily be avoided or at least minimised.
So, the main question remains, can those hard-headed users justify their 'needs' for you to put an entire company at risk? I don't think so.
Unless these guys are top level, ignore them, see what happens.
From your text I gather you must be young and pretty new to IT (correct me if I'm wrong), so it is normal they want to twist your hand to get it their way. As said above, stand up to them, YOU know better (even if you wouldn't).
If you are responsible, then YOU decide.
Bottom line: tell higher up the only solution is to keep these people in the office and work 24/24 7/7!
Marc
If 'something' 'somewhere' gives 'some' error, expect random guesses or no replies at all. Please specify details.
Free Tip: The F1 Key does NOT destroy your PC!