Great list, @Kfawcett!
I’ve not mentioned it here, but I have had problems very recently with Sendgrid and it seems that Sendgrid has a big problem with deliverability to many domains.
The source of the issue is that some email systems – very notably Apple’s (so icloud.com, me.com, etc.) – apparently look at the ‘return path’ setting rather than the ‘from’ setting as part of determining the sending domain.
Sendgrid sets ‘return path’ to a special address to handle bounces, spam reports, etc. And this address is not the same as the ‘from’ address.
What happens is that Apple’s email system looks at this return path and says, “This sender does not exist, so we should not deliver this email.” And, in fact, the email just goes into the bitbucket.
Now, Sendgrid insists that it is Apple’s email system that is doing the wrong thing (and I would tend to agree with Sendgrid). However, Apple seems to have no intention of changing this, so it’s kind of on Sendgrid to work out some sort of solution on their end (email deliverability being their whole business, of course)… Or to convince Apple to fix their systems.
Sendgrid does have a solution, but it breaks a bunch of Sendgrid features:
The only solution Sendgrid offers for this is that – upon request – they can turn on an internal setting for ‘preseve sender’ – which causes the ‘return path’ to match the ‘from’ setting… thus getting around the Apple problem.
The downside to this solution, however, is that it breaks other aspects of Sendgrid (specifically, Sendgrid can no longer automagically handle bounces and spam reports, which is of course absurd).
So, I’ve been casually looking for a new solution here.
I don’t know what explains the fact that the entire Sendgrid user base isn’t up-in-arms about this issue. But Sendgrid is – at present – entirely unacceptable as an email delivery system. It’s so weird.
(And thanks, @antony for bringing this up! I’d be interested to hear from other @Bubble users that have experienced this. Pretty much for months, I had been unable to reliably email Apple’s domains.)