Use persistent SMTP connection for bulk emails, add List-Unsubscribe header

app/blueprints/admin/email.py

@@ -21,7 +21,7 @@ from wtforms import TextAreaField, SubmitField, StringField
 from wtforms.validators import InputRequired, Length
 
 from app.markdown import render_markdown
-from app.tasks.emails import send_user_email
+from app.tasks.emails import send_user_email, send_bulk_email as task_send_bulk
 from app.utils import rank_required, addAuditLog
 from . import bp
 from ...models import UserRank, User, AuditSeverity
@@ -70,8 +70,7 @@ def send_bulk_email():
 
 		text = form.text.data
 		html = render_markdown(text)
-		for user in User.query.filter(User.email.isnot(None)).all():
-			send_user_email.delay(user.email, user.locale or "en", form.subject.data, text, html)
+		task_send_bulk.delay(form.subject.data, text, html)
 
 		return redirect(url_for("admin.admin_page"))
 

app/models/users.py

@@ -309,6 +309,11 @@ class EmailSubscription(db.Model):
 		self.blacklisted = False
 		self.token = None
 
+	@property
+	def url(self):
+		from ..utils import abs_url_for
+		return abs_url_for('users.unsubscribe', token=self.token)
+
 
 class NotificationType(enum.Enum):
 	# Package / release / etc

app/tasks/emails.py

@@ -14,9 +14,10 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+from typing import Dict
 
 from flask import render_template, escape
-from flask_babel import force_locale, gettext
+from flask_babel import force_locale, gettext, lazy_gettext
 from flask_mail import Message
 from app import mail
 from app.models import Notification, db, EmailSubscription, User
@@ -36,6 +37,10 @@ def get_email_subscription(email):
 	return ret
 
 
+def gen_headers(sub: EmailSubscription) -> Dict[str,str]:
+	return {"List-Help": f"<{abs_url_for('flatpage', path='help/faq/')}>", "List-Unsubscribe": f"<{sub.url}>"}
+
+
 @celery.task()
 def send_verify_email(email, token, locale):
 	sub = get_email_subscription(email)
@@ -43,7 +48,7 @@ def send_verify_email(email, token, locale):
 		return
 
 	with force_locale(locale or "en"):
-		msg = Message("Confirm email address", recipients=[email])
+		msg = Message("Confirm email address", recipients=[email], extra_headers=gen_headers(sub))
 
 		msg.body = """
 				This email has been sent to you because someone (hopefully you)
@@ -67,7 +72,7 @@ def send_unsubscribe_verify(email, locale):
 		return
 
 	with force_locale(locale or "en"):
-		msg = Message("Confirm unsubscribe", recipients=[email])
+		msg = Message("Confirm unsubscribe", recipients=[email], extra_headers=gen_headers(sub))
 
 		msg.body = """
 					We're sorry to see you go. You just need to do one more thing before your email is blacklisted.
@@ -80,33 +85,33 @@ def send_unsubscribe_verify(email, locale):
 
 
 @celery.task(rate_limit="25/m")
-def send_email_with_reason(email: str, locale: str, subject: str, text: str, html: str, reason: str):
+def send_email_with_reason(email: str, locale: str, subject: str, text: str, html: str, reason: str, conn: any):
 	sub = get_email_subscription(email)
 	if sub.blacklisted:
 		return
 
 	with force_locale(locale or "en"):
-		from flask_mail import Message
-		msg = Message(subject, recipients=[email])
+		msg = Message(subject, recipients=[email], extra_headers=gen_headers(sub))
 
 		msg.body = text
 		html = html or f"<pre>{escape(text)}</pre>"
 		msg.html = render_template("emails/base.html", subject=subject, content=html, reason=reason, sub=sub)
-		mail.send(msg)
+		if conn:
+			conn.send(msg)
+		else:
+			mail.send(msg)
 
 
 @celery.task(rate_limit="25/m")
-def send_user_email(email: str, locale: str, subject: str, text: str, html=None):
-	with force_locale(locale or "en"):
-		return send_email_with_reason(email, locale, subject, text, html,
-				gettext("You are receiving this email because you are a registered user of ContentDB."))
+def send_user_email(email: str, locale: str, subject: str, text: str, html=None, conn=None):
+	return send_email_with_reason(email, locale, subject, text, html,
+			lazy_gettext("You are receiving this email because you are a registered user of ContentDB."), conn)
 
 
 @celery.task(rate_limit="25/m")
 def send_anon_email(email: str, locale: str, subject: str, text: str, html=None):
-	with force_locale(locale or "en"):
-		return send_email_with_reason(email, locale, subject, text, html,
-				gettext("You are receiving this email because someone (hopefully you) entered your email address as a user's email."))
+	return send_email_with_reason(email, locale, subject, text, html,
+			lazy_gettext("You are receiving this email because someone (hopefully you) entered your email address as a user's email."))
 
 
 def send_single_email(notification, locale):
@@ -115,7 +120,7 @@ def send_single_email(notification, locale):
 		return
 
 	with force_locale(locale or "en"):
-		msg = Message(notification.title, recipients=[notification.user.email])
+		msg = Message(notification.title, recipients=[notification.user.email], extra_headers=gen_headers(sub))
 
 		msg.body = """
 				New notification: {}
@@ -187,3 +192,10 @@ def send_pending_notifications():
 			send_notification_digest(to_send, user.locale or "en")
 		elif len(to_send) > 0:
 			send_single_email(to_send[0], user.locale or "en")
+
+
+@celery.task()
+def send_bulk_email(subject: str, text: str, html=None):
+	with mail.connect() as conn:
+		for user in User.query.filter(User.email.isnot(None)).all():
+			send_user_email(user.email, user.locale or "en", subject, text, html, conn)

app/templates/emails/base.html

@@ -59,7 +59,7 @@
 				<p>
 					{% block footer %}
 						{{ reason }} <br>
-						<a href="{{ abs_url_for('users.unsubscribe', token=sub.token) }}">
+						<a href="{{ sub.url }}">
 							{{ _("Unsubscribe") }}
 						</a>
 					{% endblock %}