I find in our application three mail jars:

[INFO] +- info.magnolia.pur:magnolia-module-public-user-registration:jar:2.7.5:compile
[INFO] | - javax.mail:mail:jar:1.4.5:compile

[INFO] +- info.magnolia.form:magnolia-form:jar:2.7.3:compile
[INFO] | - info.magnolia:magnolia-module-mail:jar:5.5.8:compile
[INFO] | +- com.sun.mail:javax.mail:jar:1.6.2:compile

and another one via resteasy:
- org.jboss.resteasy:resteasy-multipart-provider:jar:4.6.1.Final:compile
[INFO] | | +- com.sun.mail:jakarta.mail:jar:1.6.5:compile

It would be nice if versions (and groupids) were in sync. I think the last one has the most up to date groupId/artifactid.