If you unable to activate mail service for a domain from plesk control panel try below steps.
>>First check this plesk>>domian>>mail >>mail settings >> "Activate mail service on domain" button is greyed out or not.
>> Some timed we are unable to activate the mail service if the "Activate mail service on domain" button is not greyed.
Solution.
>>Login to Plesk database:
mysql -uadmin -p`cat /etc/psa/.psa.shadow` psa
>> Find domain with disabled mail service:
mysql> select * from DomainServices where type='mail' and dom_id=(select id from domains where name='domain.tld');
You will get something like this.
+-----+--------+------+--------+---------------+----------------+
| id | dom_id | type | status | parameters_id | ipCollectionId |
+-----+--------+------+--------+---------------+----------------+
| 167 | 61 | mail | 2 | 229 | 167 |
+-----+--------+------+--------+---------------+----------------+
1 row in set (0.00 sec)
>> If the status of the mail service is not zero, then update the status with "0".
mysql> update DomainServices set status=0 where type='mail' and id=167;
That's it
