I’m not sure why anyone would want to build an email list app from scratch, when there are so many other options out there. You could use mailchimp or phplist or whatever to set up a list and a subscribe page, and then just include an external site link to it from within nextcloud.
I don’t know exactly what you are trying to do. Can you describe some more? You probably want to look for some open source self hosted equivalent to mailchimp, like phplist. I haven’t done this for a while myself so am not sure of the best option. You can install it on the same server with nextcloud.
I work for Discourse.org. If community is what you are looking for, you could self host a Discourse forum, like this one. Discourse does a good job reaching people by email and letting them reply by email.
I’m not particularly familiar with selfhosting software for mailing lists, but the suggestions in this subreddit, sound like they could possibly fit your needs…
is there a way to have SMTP with 587 STARTTLS (ssl) ?
mail server log :
Mar 9 00:28:33 mail1 postfix/submission/smtpd[889279]: connect from web2.tld.org[10.10.10.112]
Mar 9 00:28:33 mail1 postfix/submission/smtpd[889279]: lost connection after CONNECT from
web2.tld.org[10.10.10.112]
Mar 9 00:28:33 mail1 postfix/submission/smtpd[889279]: disconnect from web2.tld.org[10.10.10.112] commands=0/0
My only suggestion, would be to have an auto-create function that grabs each group folder (if any), creates a mailing list that matches that group name, and then auto includes each group’s members list into the mailing list (keep the unsubscribe function in the emails).