5 Best Open-Source Email Services in 2025

Reviews, comparison, screenshots and more for the 5 best open-source email services.

Written by

Forward Email Team

Published

7/1/25

Time to read

Less than 5 minutes

Forward Email is the best and only 100% open-source email service.

Open-Source Email Service Comparison

Email Service	Pricing	Storage	Attachments	Open-Source	Sandboxed Encryption	Unlimited Domains	Unlimited Aliases	TTI	SMTP	IMAP	POP3	API	E2EE	OpenPGP	WKD
Forward Email ⭐ Suggested Email for everyone Screenshot Website	$3/mo	10 GB pooled	50 MB	Yes	Yes	Yes	Yes	TTI	Yes	Yes	Yes	Yes	⚠️ Opt-in	Yes	Yes
Proton Mail Secure email that protects your privacy Screenshot Website	$3.99/mo	15 GB	25 MB	❌ Proton Mail claims to be open-source, but their back-end actually is closed source	No	No	No	No	❌ Requires you to download Proton Mail Bridge and forces vendor lock-in	❌ Requires you to download Proton Mail Bridge and forces vendor lock-in	❌ Proton Mail does not support POP3	No	⚠️ Proton Mail rewrites your emails	Yes	Yes
SimpleLogin Receive and send emails anonymously Screenshot Website	$4/mo	No SimpleLogin does not support storage	25 MB	Yes	No	Yes	Yes	No	No	No	No	No	⚠️ Opt-in	Yes	No
addy.io Protect your real email address using email aliases Screenshot Website	$4/mo	No addy.io does not support storage	25 MB	Yes	No	No	Yes	No	No	No	No	No	No	No	No
Tutanota Secure, green and ad-free. Email to feel good about Screenshot Website	€36/yr	20 GB	25 MB	❌ Tutanota claims to be open-source, but their back-end is actually closed-source	No	No	No	No	No	No	No	No	No	⚠️ Tutanota does not support PGP	No

Open-Source Email Service Screenshots

⭐ RecommendedOpen-source

Forward Email

⭐ Top RatedRecommended

Forward Email is an open-source email service. Its description from its website is: Email for everyone

Forward Email is an open-source email service.

Photo by Forward Email

Closed-source

Proton Mail

Proton Mail is a closed-source email service. According to their website: Secure email that protects your privacy

Proton Mail is a closed-source email service.

Screenshot by Forward Email

Open-source

SimpleLogin

SimpleLogin is an open-source email service. According to their website: Receive and send emails anonymously

SimpleLogin is an open-source email service.

Photo by Forward Email

Open-source

addy.io

addy.io is an open-source email service. Their official description reads: Protect your real email address using email aliases

addy.io is an open-source email service.

Photo by Forward Email

Closed-source

Tutanota

Tutanota is a closed-source email service. Its description from its website is: Secure, green and ad-free. Email to feel good about

Tutanota is a closed-source email service.

Photograph by Forward Email