Requires php 7.0+
Now depends on Standard Library by Xon
Fix that the email options page would always try to add another template to the "Email templates to exclude (from queueing)" option
Work-around for queued test email throwing "Instances of XF\Db\AbstractAdapter cannot be serialized or unserialized"
Require XF2.1+, suggest php 7.2+
While XF2.1 now supports retrying sending email on provider error, it gives up fairly quickly