New Mailbox Accounts on Exchange won't recieve external emails?

[AB_IT]

Hi All

 

Hoping someone can help, it's been confusing my brain for quite some time.

 

We have Exchange 2016 and it's worked fine up to a couple of weeks ago. Basically I'll create a new user in AD and add that existing user to Exchange. The issue is the new accounts can recieve emails from our same domain so internal emails and it can send them to internal emails, it can also send emails successfully to external addresses like my personal gmail.

 

When I try and then respond from an external email such as my gmail to the new account I get a bounce back. I've checked everything I can think of like Mail flow rules and on our filter but I can't find anything wrong.

 

Any help would be appreciated!

 

Thanks

[thimon]

Check in Attribute Editor in AD and look for msExchRequireAuthToSendTo If it's set to to True external users will not be able to email the account, if it's set to False external people will be able to. Might not be this, but worth a look.

[Jcx500]

You using Mimecast filtering? We had this when the password for mimecast expired in AD

[AB_IT]

Check in Attribute Editor in AD and look for msExchRequireAuthToSendTo If it's set to to True external users will not be able to email the account, if it's set to False external people will be able to. Might not be this, but worth a look.

Thank you. I've had a look and it's just set to which is what other accounts are set to and they're working fine so don't think it's this unfortunatley

 

You using Mimecast filtering? We had this when the password for mimecast expired in AD

 

We use something called TrendMicro, it was left to me from the old IT Manager here but their support has been dreadful! They're saying it's got nothing to do with them but im unconvinced.

Edited January 28, 2021 by AB_IT

[AB_IT]

I've got this error if it helps from my firewall

 

host OUR MAIL SERVER IP[OUR MAIL SERVER IP] said: 550 Rule imposed mailbox access for [email protected] refused (in reply to RCPT TO command)

[MatthewL]

Have you got any mail flows that stop students from receiving mail, does staff member need to be in a group i.e. Staff to apply policy for them to be allowed or something similar? Look at another user to compare what groups they are member of.