Comparison

Mailrelay vs MailerSend

Mailrelay and MailerSend both land on Worth it.

Mailrelay

Worth it

Confidence: Medium

Buy if you're a small business, NGO, or newsletter sender wanting free bulk email under 20,000 contacts.

Worth it

Confidence: Medium

Buy if you're a developer or small team sending app or WordPress transactional email on a budget.

Mailrelay versus MailerSend
Compare	Mailrelay	MailerSend
Verdict	Worth it	Worth it
Best for	Small businesses sending newsletters	Developers adding transactional email APIs
Who it's not for	High-volume senders past 20,000 contacts	Marketing newsletter senders
Privacy	One known CVE on its WordPress plugin (CSRF, 2023); responsible disclosure policy exists, but no dedicated security page found.^⁷	Core platform looks solid; the official WordPress SMTP plugin had a fixed CSRF vulnerability.
Support quality	No support evidence found	24/7 support promised; approval rejections handled poorly
Public sentiment	Reviewers like the price and free tier, but some Reddit users say rivals like Brevo outperform it.^⁴	Reviewers praise easy setup and low prices, but Reddit users complain about opaque sign-up rejections and some churn to simpler options.¹⁵
Biggest gotcha	Free plan caps at 20,000 contacts . list growth forces paid tiers^¹	WordPress plugin users must update past 1.0.8 to patch CSRF

High-volume senders past 20,000 contacts
Developers needing transactional SMTP/API scale . SendGrid-class tools fit better
Security-sensitive enterprises wanting public security documentation
Guess: shops needing deep ecommerce/CRM integrations