Unknown address error 550


since 3 days i can`t send or recieve emails from * or * ( its  a german company 1&1) with my account. I try different email-clients and try it also directly on the webmailer on From my other email account (*@hotmail *@gmail) it work to send/recieved. The proximus phone support says it work all fine with skynet email…

I recieved every time after sending an email an other mail from Mail Delivery System:

---------- Original Message ----------

From: Mail Delivery System <>

To: ***

Date: 01 June 2020 at 16:04

Subject: Delivery Status Notification (Failure)


The following message to < ***> was undeliverable.

The reason for the problem:

5.1.0 - Unknown address error 550-'Requested action not taken: mailbox unavailable\ninvalid DNS MX or A/AAAA resource record'

I try different adresses with my account, without success.

Because the adresses work for all other accounts, only skynet dosen`t, I believe the problem has to be on proximus side. Does someone know where i can send them a email? only thing i found is the phone support and there is no one who can help. Thank you

Kind regarts,


2 commentaires

Niveau d'utilisateur 7
Badge +5

Hello @dmitrij 

Please could you send me in private message the exact emails that are problematic?

Thanks in advance

Niveau d'utilisateur 7
Badge +5

@dmitrij thank you for the additional information. I contacted the Skynet team, I will keep you informed as soon as I have an answer