Here is how to solve the following error message: Domain has an outgoing mail hold. Message will be reattempted later.
grep the cPanel username / email address and if found remove it from the following files:
/etc/outgoing_mail_hold_users
/etc/outgoing_mail_suspended_users
/etc/email_send_limitsOr via WHM API:
whmapi1 unsuspend_outgoing_email user=USERNAME
whmapi1 release_outgoing_email user=USERNAME![Screen Shot 2020 06 23 at 09.57.51 - WARNING: [pool user_USERNAME] server reached pm.max_children setting (25), consider raising it](https://i0.wp.com/administrator.pejcic.rs/wp-content/uploads/2026/09/Screen-Shot-2020-06-23-at-09.57.51.png?resize=344%2C194&ssl=1 "WARNING: [pool user_USERNAME] server reached pm.max_children setting (25), consider raising it")
![2023 08 28 12 15 - node[175421]: pthread_create: Resource temporarily unavailable](https://i0.wp.com/administrator.pejcic.rs/wp-content/uploads/2023/08/2023-08-28_12-15.png?resize=344%2C194&ssl=1 "node[175421]: pthread_create: Resource temporarily unavailable")