Mailster plugin review and common issues

Mailster requires an external SMTP or transactional email service. In Mailster → Settings → Email Service, configure your provider: Amazon SES (most cost-effective for high volume), SendGrid, Postmark, or Mailgun. Enter the API key or SMTP credentials. Test the connection within Mailster settings. Common issues: (1) the configured SMTP credentials are invalid or expired; (2) the “From” email domain is not verified/authenticated in the SMTP provider; (3) the sending domain lacks SPF, DKIM, and DMARC records; (4) the email service account has a sending limit that has been reached.

Mailster automations use WordPress cron for scheduling. Check: (1) WordPress cron is running reliably — set up a true server cron to trigger wp-cron.php every minute for time-sensitive automations; (2) in Mailster → Automations → [automation], verify the trigger condition (new subscriber to specific list); (3) the automation must be active (not paused); (4) new subscribers must be confirmed (if using double opt-in, they must click the confirmation link before automations trigger); (5) check Mailster’s campaign queue for any stuck or errored items.

CSV import failures occur when: (1) the CSV has a BOM (byte order mark) or incorrect encoding — use UTF-8 without BOM encoding; (2) the email column header does not match Mailster’s expected format — download Mailster’s sample CSV to verify the expected column names; (3) the CSV contains invalid email addresses that Mailster rejects; (4) a PHP memory limit is being exceeded for very large import files — break the import into smaller batches (max 5,000 records per import); (5) duplicate emails are silently skipped — check if the subscribers already exist in Mailster.

Mailster integrates with WooCommerce to trigger automations on purchase events. In Mailster → Automations, create a new automation with trigger “WooCommerce Order Completed.” Configure the email sequence: Email 1 (immediate): thank-you for purchase + link to download/access; Email 2 (3 days later): tutorial or usage tips for the purchased product; Email 3 (7 days later): request for review or testimonial. Each email in the sequence is a Mailster template. Map WooCommerce order data to Mailster personalization fields ({firstname}, {product_name}, {order_total}).

In Mailster → Campaigns → New Campaign, select “Auto Post Newsletter” as the campaign type. Configure the RSS feed URL (your blog’s RSS feed at yourdomain.com/feed/) and set the trigger: send when a new post is published, or send a digest of new posts weekly. Choose the email template and configure which lists receive the campaign. Mailster monitors the RSS feed and automatically creates and sends a campaign when new content matches the configured trigger. This automates the blog-to-newsletter workflow without manual campaign creation.

For very large lists (50,000+ subscribers), Mailster’s flat-rate pricing becomes cost-effective compared to MailPoet’s subscriber-based plans. MailPoet’s advantages are its optional built-in sending service (no separate SMTP configuration needed), more active development, and a larger community. Mailster’s advantages are the one-time license model, CodeCanyon availability, and better WooCommerce e-commerce automation for self-hosted setups. For a list under 10,000 subscribers, MailPoet’s user experience and included sending service make it the easier choice. Above 50,000 subscribers where SMTP cost is acceptable, Mailster’s unlimited subscriber model provides better value.

Yes — Mailster’s Amazon SES integration is one of its most popular configurations. Amazon SES charges approximately $0.10 per 1,000 emails (plus minimal data transfer costs), making it extremely cost-effective for high-volume sending. Configure SES in AWS Console (verify your sending domain, set up DKIM, enable production sending), then enter the SES SMTP credentials or API key in Mailster → Settings → Email Service → Amazon SES. For 100,000 emails/month, SES costs approximately $10 vs Mailchimp’s $150+ for the equivalent subscriber count.

Yes, that can happen, especially on older sites with many plugins. This usually happens when the plugin, theme, and add-ons are updated out of sequence. In most cases, testing on staging catches the issue before it reaches the live site. From experience, backups and changelog reviews save a lot of cleanup time.

Start by checking whether another plugin already does the same job. In most cases, overlap is what creates avoidable conflicts and performance issues. A common issue is installing a plugin because it looks convenient without checking the stack first. From experience, a short compatibility review avoids most of the pain later.