Its a hidden setting and can be set in below ways
Add below line in civicrm.settings.php
$civicrm_setting['Mailing Preferences']['simple_mail_limit'] = '100';
Via drush or cv
cv api Setting.create simple_mail_limit=100
drush cvapi Setting.create simple_mail_limit=60
SET value = '100'
WHERE name = 'simple_mail_limit';
If your event has more than 50 participants, then you could install the 'Transactional Email' extension, (nz.co.fuzion.transactional), which allows you to send emails using CiviMail to search results. We use this for many purposes.
It has really helped us to be able to send an email to event participants/members, using the full capabilities of CiviMail - ...
I haven't found the cause, but I've found a fix that seems to work.
If I call up Edit on a contact and then Save it, even without making any changes, I am able to send that contact bulk email. I cannot be sure, but I suspect that the defective contact records were ones that were imported via CSV from another platform with an older CiviCRM release.
Yes, this ...