Recently Google/Outlook and a lot of the major mail servers have been configured to check for SPF / DKIM records when receiving emails to spam box the spoof emails that alot of business get.
What this means that sending emails using wp_mail function are not practical, to set up a GSuite business account / outlook account you would need to include DKIM and SPF records securing that domain name, so any email leaving using that domain and no spf/dkim will be considered as a spoof attempt and will end up in junk mail.
An easy way to get around this is setup wordpress to send emails through a specific SMTP (i.e smtp.gmail.com or smtp.office365.com or the other SMTP address from major mail platforms).
THere seems to be an issue with CRED with the SMTP plugins, once installed it does not send any emails (tested other contact form suppliers and seems to be working fine).
My suggestion would be to include SMTP settings into CRED i.e by default you can send your emails using WP_mail or enable SMTP etc...
As i understand some features might not be "functional" with SMTP i.e sending with different from addresses (but technically the people who need to use that feature will not need to use the SMTP feature) OR somehow allow us to extend it with php function etc.
Do you have any particular SMTP email plugins in mind that you have found *don't* work with Toolset Forms?
The form emails work with the standard WP mail functions, and my understanding of how the SMTP plugins typically work is to hook into the standard mail functions and take over, rather than requiring the users to use custom functions to send emails.
In which case if Toolset Forms are not sending messages when you use such a plugin the first step would be to confirm that and understand why.
I had another ticket with notification problems and they were using the Easy WP SMTP plugin, so I set up a test site with this plugin and used my google SMTP server for sending emails, and everything worked correctly with Toolset Form notifications. (I had to allow access by Less Secure Apps in my google account settings).
Do you want to test that and see if you have problems? Make sure that sending a test email from the plugin settings page works ok to confirm no authentication problems.
I'll have to see if I can set up another test with something other than Gmail, but given that it works fine with Gmail and that the process goes something like CRED sends email via wp_mail, plugin hijacks wp_mail to send via SMTP, I'm not sure how it not working with Office365 would be down to CRED.
Can you make sure you have something like WP Mail Logging installed which will log attempts to send emails, and if there is an error in sending the message it should be reported (though it won't report any delivery issues).
I did install WP Mail Log, and it does show the email there with no error.
But:
I send a test email from WP Mail SMTP goes through
I send a test email from CRED notification test it doesn't go through
I send email using CRED front end it doesn't go through
I sent email using contact form 7 it goes through.
I am not sure why you would need t rely on a third-party app to implement SMTP settings I would suggest it being built in or extended.
I was just going to say that I just set up a test live.com account to test this with the Outlook SMTP servers, and it appears to be working correctly.
I'm using the Easy WP SMTP plugin.
If the other plugin you are trying doesn't work then I'd suggest you switch to Easy WP SMTP, unless that is not an option.
Toolset wouldn't consider developing a bespoke SMTP mailing system when there are existing plugins that already do this very well, it wouldn't be a good use of our resources given the other features we would like to prioritise.
Not saying that you should build a separate plugin for this, but in the settings TAB of CRED it would be useful to have that option and not rely on third-party plugins. It doesn't really require that much change as well, because you would still be using the same exact function wp_mail that you have, instead define the outgoing server / user / pass and security option rather than use the default server option which 90% of the time will lead it to go to the spam box.
