We want SharePoint to send an email on every 1st day of the month as a reminder.
Is it possible to do that in the SharePoint Designer or SharePoint site?
If it is SharePoint online site , By using "Microsoft flow" concept we can schedule mails(as required daily , monthly or particular day).
Please refer Flow to schedule mails
You can create a monthly alert in SharePoint with retention policy and workflow.
Create a SharePoint 2010 platform to send an email.
Then add the retention policy to your list by going into List Settings and clicking Information management Policy Setting. Create retention policy like the following:
For more detailed information, refer to the following article about creating a monthly alert in SharePoint with retention policy and workflow: