Troubleshooting: SMTP Error (550): Failed to add recipient (5.1.1 address rejected: User unknown in virtual alias table)

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#1 Sun, 11/24/2019 - 12:12
rkan

Troubleshooting: SMTP Error (550): Failed to add recipient (5.1.1 address rejected: User unknown in virtual alias table)

Hi this problem has bogged me down, and I noticed there were few these 550 5.1.1 errors already in forum. Unfortunately haven't found the solution.

This has do with one email address, which uses a 3rd party email solution provider: user@example.com, that gives me the error when I try to send from user@ejemplo.com. error message: SMTP Error (550): Failed to add recipient "user@example.com" (5.1.1 user@example.com: Recipient address rejected: User unknown in virtual alias table).

Background (this is probably important): Both example.com and ejemplo.com are hosted on my virtualmin, they were recently migrated here, so I wonder if there is a local conflict? In short:

  • Both example.com and ejemplo.com are hosted on my domain
  • example.com uses a 3rd party email service
  • ejemplo.com uses roundcube on virtualmin
  • sending a message from user@ejemplo.com to example.com gives the error message above.
  • sending messages to other emails (gmail etc) works fine from user@ejemplo.com
  • when user@ejemplo.com was not hosted on virtualmin, it sent messages to user@example

Thanks for any insights! Definitely contacting my email provider for example.com, but I want to understand the underlying issue here.

thanks so much.

Sun, 11/24/2019 - 13:50
Dibs

@rkan: Have you tried sending emails to user@ejemplo.com from a gmail\hotmail\yahoo type of account?

Mon, 11/25/2019 - 14:48
rkan

Thanks Dibs - and good point. Yes, I can send emails to other gmail/hotmail etc accounts, I can also receive email from user@example.com into the ejemplo.com account; the sending seems to be the issue here. I've done an https://mxtoolbox.com/domain/example.com/ check and their are no errors. I also used various other emails to send emails to example.com, and they work without the 550 5.5.1

For lack of a better way of describing it, could it be some sort of caching issue? If so is there a way to check this? It seems localised.

Mon, 11/25/2019 - 15:47
Dibs

@rkan,

I'm slightly confused.

  1. Can you send emails TO user@ejemplo.com FROM gmail etc? Are they received?
  2. Can you send email FROM user@ejemplo.com TO gmail etc? Are they received?
  3. Can you send emails TO user@example.com FROM gmail etc? Are they received?
  4. Can you send email FROM user@example.com TO gmail etc? Are they received?
  5. Can you send emails TO user@example.com FROM user@ejemplo.com? Are they received?
  6. Can you send email FROM user@ejemplo.com TO user@example.com? Are they received?
Mon, 11/25/2019 - 16:44 (Reply to #4)
rkan

apologies:

  1. Can you send emails TO user@ejemplo.com FROM gmail etc? Are they received? Can send/received
  2. Can you send email FROM user@ejemplo.com TO gmail etc? Are they received? Can send/received
  3. Can you send emails TO user@example.com FROM gmail etc? Are they received? can send/received
  4. Can you send email FROM user@example.com TO gmail etc? Are they received? can send/received
  5. Can you send emails TO user@example.com FROM user@ejemplo.com? Are they received? sending gets the 550 5.1.1 errors, can receive from user@example.com
  6. Can you send email FROM user@ejemplo.com TO user@example.com? Are they received? No this gets the 550 5.1.1, and does not allow me to send the message (its a popup warning). Not received.

for 1-4, I used a gmail account and a google apps account to test.

Tue, 11/26/2019 - 05:14
Dibs

@rkan - so from what you are saying:

Can you post up your postfix configuration? And for the example.com - mail is NOT enabled for that VirtualServer?

Tue, 11/26/2019 - 08:59
rkan

And for the example.com - mail is NOT enabled for that VirtualServer?

my god, after all that, this was the issue! I really appreciate your patience here, its an obvious rookie mistake.

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