We won't be able to deliver this message...

[Koldov]

Bit confusing so I will number the accounts 1, 2 & 3

 

1 = New account (domain/tenant - not new, but just created mail on it yesterday) setup DNS for SPF, DKIM and DMARC (all OK except for DMARC).

2 = LGfL mail account

3 = Other O365 account

 

As the title says, this error appears when entering the email address FOR account 1, FROM account 2 (in Outlook or Webmail), if I send anyway it comes back as undeliverable...

 

 

I can receive emails FROM account 1, TO account 2, however if I reply to the email I just received... same thing - undeliverable!

 

I can also send to and receive from that address from other email accounts, account 1 to 3 and 3 to 1.

 

Just to note, the account I cannot send from is LGfL and I'm not sure if they use a full O365 backend, or Exchange, or if that even makes a difference as I guess it's basically all the same thing.

 

I have removed auto-complete in Outlook and unticked 'cached mode' ( neither had any affect ), but as this also happens from account 2 when I access it on the web to account 1 , so I don't think it's an Outlook client issue.

[TechMonkey]

Sounds like a cached address on that account somehow. Try manually typing out the address fully. Then try selecting from the address book.

[Koldov]

Yeah done both of those and that's what my research has led me to, hence this bit...

 

I have removed auto-complete in Outlook and unticked 'cached mode' ( neither had any affect ), but as this also happens from account 2 when I access it on the web to account 1 , so I don't think it's an Outlook client issue.

 

So I thought I'd done what I needed to clear any kind of cache at my end and as it's an LGfL mail account, I can't really see where else I could look for this

[Koldov]

AHHHHHHHH!!!! Think I've found it!

 

DNS records for the domain had an email forwarding section that I must have set up many years ago... I guess it was to initially route any emails to that user on that tenant/domain to an email address that I actually use.

 

I presume that sent the email into a bit of a loop considering I was sending from account 2 to account 1 and yet the DNS for account 1 had a record to forward anything sent to account 1 to account 2... confusing!

 

Anyway, I've deleted that record so I'll give it an hour or two and see if it's fixed.