Mailmeteor is a mail-merge tool that sends personalised emails from your own Gmail or Outlook account, with your list in Google Sheets. It tracks opens on every plan, and its Premium and Professional plans add follow-ups that go out when someone hasn't replied. Daily limits run from 50 emails on the free Hobby plan to 2,000 on Professional.
People look for alternatives for three reasons: they need more sending volume than their plan allows, they want a different spreadsheet or campaign workflow, or their outreach has shifted from sending one email to many people toward following up with a smaller number of named prospects. These five alternatives are grouped by which of those you're solving.