Start from events, not from student count
Five thousand students does not mean 5,000 emails. Transactional volume comes from events: someone enrolls, pays, renews, fails a payment, forgets a password or finishes a course. Count the events per month, multiply by the number of emails each event triggers, and only then look at a price list.
The assumptions below are ours, not vendor figures. They describe a mixed course business: 5,000 student accounts, 150 new enrollments in an ordinary month, 1,000 students on a monthly membership, a 5% payment-failure rate and a 5% monthly password-reset rate. Replace each number with your own from your LMS, payment processor and mail logs before you trust the totals.
Weekly lesson reminders are listed separately because they are the single largest line and because they are arguably not transactional at all. The FTC's CAN-SPAM guide treats transactional or relationship messages narrowly, covering messages that complete or confirm a transaction, give safety or security information, report changes in terms or account standing, or deliver goods or services already agreed to. A nudge to come back to a lesson may sit closer to a subscribed or marketing message, which matters for unsubscribe handling.
| Event (our assumption) | Events per month | Emails per event | Emails per month |
|---|---|---|---|
| New enrollment: account, receipt, welcome | 150 | 3 | 450 |
| Membership renewal receipt | 1,000 | 1 | 1,000 |
| Failed payment and two retry notices (5% of 1,000) | 50 | 3 | 150 |
| Password reset (5% of 5,000) | 250 | 1 | 250 |
| Completion or certificate email | 100 | 1 | 100 |
| Lean total | 1,950 (23,400 a year) | ||
| Optional weekly lesson reminder to all 5,000 | 4 sends | 5,000 | 20,000 |
| Total with reminders | 21,950 (263,400 a year) |
What the published tiers cost at these volumes
Prices below were read from each vendor's pricing page on 30 October 2026. Amazon SES lists $0.10 per 1,000 outbound emails under its a la carte pricing, where you pay only for what you use, plus $0.12 per GB of attachment data; it also sells Essentials, Pro and Enterprise plans, which this estimate does not use. Postmark lists Basic at $15 a month and Pro at $16.50 a month, each starting at 10,000 emails, with overage of $1.80 and $1.30 per 1,000. Mailgun lists Basic from $15 a month with 10,000 emails and overage from $1.80 per 1,000, and Foundation at $35 a month with 50,000 emails after a free first month.
Where a total needs overage, we multiplied the published per-1,000 rate by the extra thousands. Postmark's page describes plans as starting at 10,000 emails, so a larger preset tier may cost less than Basic plus overage; treat the overage figure as a ceiling and check the volume slider before you buy.
| Service and plan | Lean case: 1,950 a month | With reminders: 21,950 a month | Notes from the pricing page |
|---|---|---|---|
| Amazon SES, a la carte pricing | $0.20 a month, about $2.34 a year | $2.19 a month, about $26.34 a year | $0.10 per 1,000; attachments $0.12 per GB; new accounts start in a sandbox |
| Postmark Basic | $15 a month, $180 a year | $36.51 a month, $438.12 a year with overage | Overage $1.80 per 1,000; 45 days of data retention |
| Postmark Pro | $16.50 a month, $198 a year | $32.03 a month, $384.42 a year with overage | Overage $1.30 per 1,000; retention add-on from $5 a month |
| Mailgun Basic | $15 a month, $180 a year | $36.51 a month with overage from $1.80 per 1,000 | 1 day of log retention |
| Mailgun Foundation | $35 a month after a free first month: $385 in year one, $420 in a full paid year | $35 a month after the free first month; 50,000 included | 5 days of log retention |
| Postmark free developer plan | Not enough: 100 emails a month | Not enough | No overage allowed |
| Mailgun Free | Risky: 100 emails a day | Not enough | Renewal-day spikes exceed the daily cap |
Why the cheapest line is not automatically the right one
Amazon SES is cheaper by an order of magnitude at these volumes, but the price buys a sending pipe, not a finished product. AWS documents that new SES accounts start in a sandbox, limited to verified recipients, 200 messages per 24 hours and 1 message per second, and that AWS Support gives an initial response to a production-access request within 96 hours. You also agree to have a process for bounce and complaint notifications. For a solo course owner that is setup time, not a monthly fee, but it is real.
Log retention is the hidden difference between the $15 plans. Mailgun Basic keeps 1 day of logs and Postmark keeps 45 days. When a student says the receipt never arrived three weeks after a renewal, a 1-day log cannot answer the question. If you handle your own support, retention is worth more than a few dollars a month.
Spikes matter more than averages. The lean case averages about 65 emails a day, but most membership renewals in our example land on the same billing day. A daily cap such as Mailgun Free's 100 emails a day fails on exactly the day you most need receipts to arrive.
- Pick SES if you or a contractor will set up domain verification, the production-access request and bounce handling, and you want the lowest running cost.
- Pick a $15 to $17 managed plan if you want a dashboard, searchable logs and fewer moving parts, and your volume stays near the lean case.
- Pick a 50,000-email plan only if you will send reminders to the whole student base; otherwise you pay for headroom you will not use.
Do not send this volume through your web host
Host mail is usually capped well below these numbers. Kinsta's documentation lists up to 150 transactional emails a day on its Single 35k, 65k and WP 2 plans, up to 1,000 on mid-tier plans and up to 3,000 on the largest, shared across all sites on the plan. Kinsta also says its transactional email service does not support DMARC alignment and recommends a third-party SMTP service if you need DMARC compliance.
A weekly reminder to 5,000 students cannot go out in one day on any of those caps, and renewal-day receipts for 1,000 members exceed the 150-a-day tier. If your plan is in that range, a dedicated sending service is not an upgrade; it is a requirement.
The Gmail threshold and what it changes
Google's sender guidelines apply stricter rules to senders who send more than 5,000 messages a day to Gmail accounts: SPF, DKIM and DMARC on the sending domain, From-domain alignment, and one-click unsubscribe on marketing and subscribed messages. All senders must set up SPF or DKIM, keep the reported spam rate below 0.3% and use valid forward and reverse DNS and TLS.
At 5,000 students you are unlikely to cross 5,000 messages a day to Gmail alone unless a reminder and a launch announcement land on the same day. Set up SPF, DKIM and DMARC anyway; every service above supports it, and it is the cheapest deliverability work you will do. If you send lesson reminders, give them an unsubscribe link even if you consider them transactional.
Worked checklist: estimate your own bill in 15 minutes
- Export last month's new enrollments, renewals and failed payments from your LMS and payment processor.
- Count password resets from your mail log or SMTP plugin log if it keeps one.
- List every automated email your LMS sends per event, including admin copies you receive yourself.
- Add any reminder or drip notifications and decide whether each is transactional or subscribed.
- Find your busiest single day (usually the renewal date or launch day) and compare it with any daily cap.
- Price the monthly total on two services and add attachment size if receipts are sent as PDFs.
- Write down the log retention you need to answer a "never received it" ticket and check each plan against it.
Questions before you decide
How many emails a month does a 5,000-student course site send?
In our worked example, about 1,950 a month for receipts, enrollments, payment failures, password resets and certificates, and about 21,950 if a weekly reminder goes to every student. Your own figure depends on enrollments, renewals and reminders, not on the size of the student list.
Is Amazon SES really that much cheaper?
At published rates, yes: $0.10 per 1,000 emails means about $26 a year even for the reminder case. New accounts start in a sandbox capped at 200 messages a day, and AWS says it responds to production-access requests within 96 hours, so request access well before a launch.
Can I just use my host's mail for receipts?
Usually not at this volume. Kinsta, for example, documents a 150-a-day cap on its entry plans and no DMARC alignment for host-sent mail. A renewal day with 1,000 receipts would exceed that cap.
Sources & verification
Product details and prices can change. Check the linked provider before buying.
- Amazon SES: pricing Accessed 30 Oct 2026
- Amazon SES developer guide: request production access Accessed 30 Oct 2026
- Postmark: pricing Accessed 30 Oct 2026
- Mailgun: pricing Accessed 30 Oct 2026
- Kinsta: transactional email Accessed 30 Oct 2026
- Gmail Help: email sender guidelines Accessed 30 Oct 2026
- FTC: CAN-SPAM Act compliance guide for business Accessed 30 Oct 2026
Sources link directly to providers. Product buttons may use separately labeled affiliate links. Read our disclosure.