Unable to activate the mail service on a domain: mailmng-outgoing failed: ERROR:main:UNIQUE constraint failed: vhost_ids.guid

Aleksandar Stoev

Updated January 13, 2026 19:14

kb: technical

Symptoms

Mail service cannot be activated on example.com. One of the following errors is displayed:

PLESK_ERROR: mailmng-outgoing failed: ERROR:__main__:UNIQUE constraint failed: vhost_ids.guid

PLESK_ERROR: mailmng-outgoing failed: ERROR:__main__:NOT NULL constraint failed: vhost_ids.domain_id

Cause

An orphaned entry with the guid of example.com already exists in the vhost_ids table of the outgoing mail limits /var/lib/plesk/mail/outgoing/data.db database.

Resolution

One domain is affected

Connect to the server via SSH
Enable debug.
Reproduce the error.
Find the following entry in /var/log/plesk/panel.log:

CONFIG_TEXT: #7 /opt/psa/admin/plib/Mail/AbstractFacade.php(1670): Service_Driver_Mail_Plesk_Domain_Unix->addVhostId(string 'example.com', string '22ddab34-a039-4ef1-9f4c-cbeba73463fb')
Disable debug.
Backup the outgoing mail database:

# cp /var/lib/plesk/mail/outgoing/data.db{,.bkp}
Open the outgoing mail database:

# sqlite3 /var/lib/plesk/mail/outgoing/data.db
Check if the entry with guid from step 4 is in there:

# sqlite> select * from vhost_ids where guid="22ddab34-a039-4ef1-9f4c-cbeba73463fb";
22ddab34-a039-4ef1-9f4c-cbeba73463fb|49
Check if it is orphaned(no domains with such id's in the domains table):

# sqlite> select * from domains where id=49
Resolve the inconsistency:
- If the output in step 9 was empty, remove the orphaned entry from the vhosts_ids table:
  
  # sqlite> delete from vhost_ids where guid="22ddab34-a039-4ef1-9f4c-cbeba73463fb";
- If the output in step 9 was not empty, apply the below solution from the "Multiple domains are affected" section.

Multiple domains are affected

Connect to the server via SSH
Backup the outgoing mail control database:

# cp /var/lib/plesk/mail/outgoing/data.db{,.bkp}
Wipe the outgoing mail control database:

# plesk sbin mailmng-outgoing --destroy
Recreate it:

# plesk sbin mailmng-outgoing --init