Typically, if you’re sending any volume of email or sending emails to visitors you’ll want to use a third-party. Sometimes, you only need to send yourself notifications and are having deliverability problems with these notifications – this is the case, where you may want to send your emails through Gmail’s SMTP.
On Tuesday October 9, 2018 my G Suite Catch-All Email Address stopped working. Fortunately, I noticed rather quickly and found the best way to enable it again was to “turn it off, and back on again”. I’ve made notes about exactly how I did that in case others (or future me), finds it necessary.