Using s-nail instead of heirloom-mailx to send emails

[ttionya]

The tool for sending emails, heirloom-mailx, has been removed in Alpine v3.18.

Please refer to the issue (https://gitlab.alpinelinux.org/alpine/aports/-/issues/14791) and commit (https://gitlab.alpinelinux.org/alpine/aports/-/commit/8f375abf662d2f84ff9b132e8710d6e25eeaf80f) in the Alpine/aports repository for more details.

Although it is possible to lock the Alpine version at 3.17, it is not an ideal solution. I prefer to continue using rclone as the base image, so we need to replace the email sending tool.

I plan to replace heirloom-mailx with s-nail because heirloom-mailx is a stub for s-nail. s-nail maintains a high degree of compatibility, although there may be some incompatible parts, the main options are compatible.

This change will take effect in the next version, and I am currently testing it.

The changes have taken effect in v1.19.0. Here is the s-nail documentation.

[ttionya]

To avoid introducing disruptive changes to the backup tool, I will lock the s-nail version to v14.9.x. If in the future Alpine cannot provide an APK package for v14.9, we will compile and install s-nail ourselves.

[ttionya]

Starting from v14.10 and future v15 versions, s-nail will adopt a new MTA (Mail-Transfer-Agent) credential, and users will be alerted to switch to the new credential promptly. As we will maintain s-nail v14.9, users can DISREGARD warning messages similar to the following.

mail: Warning: variable superseded or obsoleted: smtp
mail: Warning: variable superseded or obsoleted: smtp-auth-user
mail: Warning: variable superseded or obsoleted: smtp-auth-password
mail: Obsoletion warning: please do not use *smtp*, instead assign a smtp:// URL to *mta*!
mail: Obsoletion warning: Use of old-style credentials, which will vanish in v15!
mail:   Please read the manual section "On URL syntax and credential lookup"

Of course, you can switch to using MTA credentials on your own to eliminate the warning messages. Here's a simple conversion example:

# For Zoho
-S smtp-use-starttls \
-S smtp=smtp://smtp.zoho.com:587 \
-S smtp-auth=login \
-S [email protected] \
-S smtp-auth-password=mypassword \
-S [email protected]

# Convert to MTA
-S v15-compat
-S smtp-use-starttls
# @ => %40
-S mta=smtp://abc%40example.com:[email protected]:587
-S smtp-auth=login
-S [email protected]

[kevdogg]

Hey I just wanted to chime in here a give another example for those that might want to avoid errors in the logs. I'm using arch linux as the client. SSL CA certs are located in /etc/ssl/certs (which I think is pretty standard for most linux distributions (although tls-ca-file could be used as an alternative to tls-ca-dir). The configuration below only used TLS 1.3 which nowadays seems to be the default with most mailers. TLS 1.2 could also be configured if needbe. I used this reference to configure s-nail for version 15: https://manpages.ubuntu.com/manpages/focal/en/man1/s-nail.1.html

-S v15-compat
-S mta=smtps://<user>:<password>@smtp.<domain>.com:465
-r bitwarden@<domain>.com(Bitwarden-Backup@archbw)
-S smtp-auth=login
-S tls-ca-dir=/etc/ssl/certs
-S tls-verify=strict
-S tls-config-pairs=Protocol=-ALL\,+TLSv1.3