v0.4.1: Improved logging, attachment removing, delivery status indicaton and more *POTENTIALLY BREAKING*

This release of go-mail brings some new features as well as some code clean up and stability improvments.

Improved logging interface (Potentially Breaking Change)

The debug logging system in go-mail has been refactored. A new custom log type Log was introduced, that includes the message direction, format and arguments. The Logger interface and the Stdlog implementation were modified to accept this new type. This change is breaking custom implementations of the Logger interface, but the new interface provides much more flexibility (#136/#141). Additionally we added support for JSON logging (#142) using the log/slog package that has been added to the stdlib in Go 1.21.

This change is breaking custom logger implementations

Removal of attachments/embeds

#147 adds support for removing all attachments/embeds/parts from a Msg. This allows to re-use a Msg and allows for replacing message parts.

The following methods can be used:

• Msg.UnsetAllAttachments()
• Msg.UnsetAllEmbeds()
• Msg.UnsetAllParts()

Thanks to @leahoop for their first PR!

Reading of multiple addresses from a single comma-separated string

#155/#152 add support for three new methods that allow to read multiple recipient addresses for the TO:, CC: and BCC: fields from a single comma-separated string.

The following methods have been added:

• Msg.ToFromString(string)
• Msg.CcFromString(string)
• Msg.BccFromString(string)

Thanks to @suntong for requesting this useful feature!

Delivery status indication for messages

With #167 we added support for delivery status indication of messages. This is especially helpful for bulk mailings to identify if a message was actually delivered or not. A helper method IsDelivered has been added that will return true after successful delivery of a Msg. Thanks to @mitar for requesting this useful feature!

Making use of best practice default ports and fallback ports

When using SSL or STARTTLS, so far the default port was always 25, which is against best practices as described in RFC8314, section 3.3. With #170 we've deprecated the WithSSL() and WithTLSPolicy options in favour of WithSSLPort(bool) and WithTLSPortPolicy(TLSPolicy).

• WithSSLPort tells the Client to use a SSL/TLS connection and automatically sets the port to 465.
• WithTLSPortPolicy tells the client to use the provided TLSPolicy and sets the correct port automatically. Port 587 is used for TLSMandatory and TLSOpportunistic. NoTLS will allways use port 25. If the connection fails with TLSOpportunistic, a plaintext connection is attempted on port 25 as a fallback.

Thanks to @muhlemmer for raising the request and providing the first part of the PR.

AUTH LOGIN extension draft

We've added support for the auth login extension draft. This effectively is a draft that expired and was deprecated in favor of the AUTH PLAIN SASL extension (#163).

Thanks to @james-d-elliott for the PR!

Code cleanup and stability

The codebase has been reviewed and a couple of potential nil pointer dereferences have been identified and fixed.
Additionally, a potential panic has been fixed in fileFromReader (#161) - thanks to @rami-dabain for their first PR!

What's Changed

• Replace hardcoded '2' in Output with const CallDepth by @wneessen in #137
• Fix nil pointer dereference in msgwriter due to missing error handling by @wneessen in #139
• Update Go version to 1.21 in GitHub workflows by @wneessen in #140
• Refactor logging for clearer messaging direction by @wneessen in #141
• #142 Add structured JSON logger and associated tests by @wneessen in #143
• #147 add remove attachments and embeds methods by @leahoop in #148
• Feature/147 add method to remove any attachmentembed by @wneessen in #149
• Add new methods and tests for handling email addresses by @wneessen in #155
• Eleminate potential null pointer exceptions by @wneessen in #157
• Added return error to fileFromReader by @rami-dabain in #161
• feat(smtp): auth login extension draft support by @james-d-elliott in #163
• Upstream sync / refine function comments to include return type GoDoc links by @wneessen in #165
• Add delivery status indication for messages by @wneessen in #167
• Update FreeBSD version in .cirrus.yml by @wneessen in #169
• Add default ports and fallback behavior for SSL and TLS by @wneessen and @muhlemmer in #170
• Add Charset support for message parts by @wneessen in #172
• Add "X-Auto-Response-Suppress" header and update SetBulk method by @wneessen in #173
• Update Go version in GitHub workflow files by @wneessen in #174

New Contributors

• @leahoop made their first contribution in #148
• @rami-dabain made their first contribution in #161
• @muhlemmer made their first contribution in #170

Full Changelog: v0.4.0...v0.4.1

v0.4.0: Custom dial contexts and OAUTH2 support

This release adds two great improvements to go-mail.

Custom dial contexts

The newly added option allows for providing custom dial contexts, to use i. e. for some more extra processes in establish a connection such as using proxy, DNS hook, and so on. The dial context can be provided via the WithDialContextFunc option on the Client. Huge thanks to @sters for their contribution to the project!

OAUTH2 support

@drakkan (Developer of the excellent SFTPGO) added a new SMTP auth option for OAUTH2 authentication tokens (aka XOAUTH2). We now support Google and Microsoft O365 OAUTH2 authentication tokens. With this, go-mail now support 4 different SMTP Auth variants: LOGIN, PLAIN, CRAM-MD, XOAUTH2.
Thanks again @drakkan for this contribution and also big thanks to @james-d-elliott for helping to test this new option and providing their broad knowledge to this feature.

Other changes

We've synced up the changes that were made to the official go net/smtp package with our own copy. So this way go-mail is fully in sync with the official go package again.

What's Changed

• Sync upstream changes to net/smtp by @wneessen in #127
• Adding WithDialContextFunc client option by @sters in #128
• add Oauth2 support by @drakkan in #130
• Preparation for the v0.4.0 release: by @wneessen in #131
• oauth2: add more test cases by @drakkan in #132

New Contributors

• @sters made their first contribution in #128
• @drakkan made their first contribution in #130

Full Changelog: v0.3.9...v0.4.0

v0.3.9 SMTP client port, debug logging and more

This release is the biggest since the initial release of the library. While there wasn't really much change on the surface, there happend a lot under the hood.

net/smtp fork

go-mail heavily relies on the Go stdlib net/smtp package. Unfortunately this lib is in feature freeze mode, so that enhancing/extending the package is not possible. This restricted us - at least to a certain degree - as we can't add features that would be useful for go-mail. For that reason we ported/forked the whole package over and adjusted all parts of go-mail to use it instead.

The original license has been imported and the license headers have been adjusted to reflect the go-mail's MIT license and the original Go BSD-3-Clause license. Additionally, the license headers have been converted to SPDX style.

Debug logging

Since we now have full control over the SMTP client part of go-mail, this allowed us to implement ldebug logging for the SMTP communication. Via the Client.WithDebugLog client option the user can enable this feature. It will then make use of the new smtp/Client.SetDebugLog method. Once the flag is set to true, the SMTP client will start logging incoming and outgoing messages to os.Stderr.

We've also implemented a simple log.Logger interface, as well as a standard logger that satisfies this interface. This allows the user to provide a custom logger, as long as the interface is stasified. If no custom logger is provided, the Stdlog will be used (which makes use of the Go stdlib again). Accordingly, a Client.WithLogger option and Client.SetLogger method have been implemented. Same applies for the smtp counterparts.

Details can be found in #102 and #115 .

More support for middlewares

With #108, #109 and #117 we provide more access to message parts (like attachments or embeds) for middlewares. Parts can now be gotten, set and deleted by middlewares.

Fix attachment reader consectuive writes

Msg.AttachReader() would not output the attached file after consecutive writes (e.g. a write to a file and then send via Client). In #111 we fixed this behaviour by first reading the io.Reader into memory and then creating a new bytes.Reader, which does support seeking. In the writeFunc we then seek to position 0 after a successful io.Copy. This is probably not the most memory efficient way of handling this, but otherwise we'll have to break the io.Reader interface, which we do not want..

To compensate this, additionally, a new way of attaching/embedding files has been added: Msg.AttachReadSeeker() and Msg.EmbedReadSeeker() which take a io.ReadSeekeras argument instead. These two methods will skip the reading into memory and make use of the Seek method of the corresponding interface instead.

We recommend to make use of the new methods instead, to make the memory footprint low.

Special thanks

Special thanks go to @Karitham, @cvette and @halilylm for reporting bugs and/or providing PRs to address issues. Also big thanks to @james-d-elliott of the Authelia project for providing helpful insights on various issues with the library.

What's Changed

• Set up FreeBSD tests via CirrusCI by @wneessen in #99
• Fork the net/smtp package from Go's stdlib into go-mail by @wneessen in #100
• Implement SMTP client debug logging by @wneessen in #102
• Update documentation and copyright headers by @wneessen in #103
• Refactor DSN handling from client.go to smtp.go by @wneessen in #104
• Introducing Msg part deletion by @wneessen in #108
• Introduce GetEmbeds() and SetEmbeds() by @wneessen in #109
• Fix Attach/EmbedReader and implement Attach/EmbedReadSeeker by @wneessen in #111
• Go1.20 workflow updates by @wneessen in #113
• Update golangci-lint to Go 1.20 by @wneessen in #114
• Implement Logger interface by @wneessen in #115
• Provide more ways for middleware to interact with mail parts by @wneessen in #117
• fix: parsing of ReplyTo with special characters by @cvette in #118
• Make golangci-lint happy again by @wneessen in #120
• Remove defer from for loops by @wneessen in #122

New Contributors

• @cvette made their first contribution in #118

Full Changelog: v0.3.8...v0.3.9

v0.3.8: Fix bug in SMTP LOGIN Auth for servers with non-normative responses

This release fixes a bug in the SMTP LOGIN Auth part of go-mail as reported in #94. The changes introduced in d0f0435 and 6a446bd caused issues with SMTP servers like ProtonMail Bridge, which respond with non-normative messages.

Thanks to @james-d-elliott from the Authelia team for the investigation and report.

What's Changed

• Fix SMTP AUTH LOGIN method for servers with uncommon success messages by @wneessen in #95

Full Changelog: v0.3.7...v0.3.8

v0.3.7: Improved delivery error handling

This release introduces the SendError type which satisfies the error interface and provides a better way to identify delivery errors. A new sendError field has been added to the Msg as well, to also allow per-message error handling in bulk mailings.

We've also added different SendErrReason that indicate the different things that can go wrong during mail delivery. These reasons can be checked for, for each Msg using the errors.Is methods. Alternatively, the errors.As method can be used to unwrap the SendError to get access to it's methods. The SendError provides a IsTemp method that returns true if the delivery error is of temporary nature.

This is useful for delivery retries. For example the following code could be used to decide whether the error is retryable or not:

	if err := c.DialAndSend(m); err != nil {
		var se *mail.SendError
		if errors.As(err, &se) && se.IsTemp() {
			// retryable error
			log.Printf("temporary error, will re-try")

			/*
			  perform some re-try logic here
			*/
		}
		// permanent error
		log.Fatal(err)
	}

If the Send method runs into more than one error during delivery, these errors are accumulated and returned with the reason ErrAmbiguous, since it's not possible to exactly say what caused the error. For this it comes handy, that the *Msg now provides per-message send errors. The *Msg now has HasSendError(), SendErrorIsTemp() and SendError(). While HasSendError() simply returns a bool in case a *Msg failed during delivery and SendErrorIsTemp() returns true if it's a temporary error, the SendError() will return the full SendError error of the corresponding *Msg.

The Error() method of SendError will return a detailed error string based on the accumulated errors that were collected during the delivery.

Thanks to @imirkin and @iwittkau for providing valueable feedback and performing code review on the PR.

What's Changed

• Introduction of new error type for sending errors by @wneessen in #91

Full Changelog: v0.3.6...v0.3.7

v0.3.6: Bugfixes and improvements

This release is mainly a bugfix release but also introduces slight improvements.

One major bugfix is in Client.Send(), not sending all mails in case an error occured during a bulk mailing. Client.Send() provides the possibility to send multiple *Msg in one go. If one of the *Msg caused an error with the sending mail server, we were returning completely, while not processing any *Msg that came after the failing message.

This release fixes this behaviour by processing each message first and then return a accumulated error in case any of the *Msg processing failed

Additionally, this release separates the Client.Send() method into two different versions. One that makes use of the new errors.Join() functionality that is introduced with Go 1.20 and one that handles it the old way for any supported version lower than Go 1.20

Also welcome @james-d-elliott as new contributor to the project, providing a bugfix in the Client.Dialer and adding an option to disable NOOP calls. Thanks for the contribution, James!

What's Changed

• Fix #85: Client.Send() failing for all messages if one is broken by @wneessen in #86
• fix: tls config unused with dialer by @james-d-elliott in #87
• feat: without noop option by @james-d-elliott in #88

New Contributors

• @james-d-elliott made their first contribution in #87

Full Changelog: v0.3.5...v0.3.6

v0.3.5: Bugfix in msgWriter error handling and GetAddrHeader

This release fixes a bug in the msgWriter error handling as well as introduces the new GetAddrHeader method. Thanks to @oschwald for both, the error report and the feature request.

• The error handling in the msgWriter.writeBody method was not working properly. We basically overwrote the mw.err with nil if the function that followed after a failed write attempt was successful again.
• SetHeader and SetHeaderPreformatted have been deprecated in favour of SetGenHeader and SetGenHeaderPreformatted As pointed out in #80 the naming was pretty confusing, given that we already have SetAddrHeader.
  With the new naming convention it should be more clear to the user, which method to use for which action. For compatibility reasons the old methods have been kept for now but in reality they are just aliases to the new methods.
• GetAddrHeader and GetAddrHeaderString have been introduced As requested in #80 analogous to GetGenHeader we also need a similar method for the address headers. Since address headers are *mail.Address pointer, we've also added a *String method that will extract the address string and return a string slice instead.
• Additionally we're introducing methods for the actual address headers: GetTo, GetFrom, GetCc and GetBcc (with a *String counterpart as well). This way the user has full flexibility. Either they use the more "low-level" GetAddrHeader method or the higher level methods for the corresponding address type

NOTE; We encourage users who use the SetHeader method in their code to switch to SetGenHeader instead.

What's Changed

• #81: Fix error handling in body writer by @wneessen in #82
• #80: GetAddrHeader and SetGenHeader by @wneessen in #83

Full Changelog: v0.3.4...v0.3.5

v0.3.4: MessageIDs and preformatted headers

This release introduces a bugfix and an enhancement:

• A bug was fixed in the MessageID generation. Due to the lack of randomness, the generated IDs for several messages might be the same. Therefore the requirement of uniqueness is not fulfilled. This has been fixed via #75
• A new methods SetHeaderPreformatted has been introduced, which allows the user to set a message header with preformated text. The header will not be altered during the mail message processing/output. More details in #77

What's Changed

• Fixed SetMessageID message ID generation by @wneessen in #75
• Add SetHeaderPreformatted() method by @wneessen in #77
• The new messageID generated with #74 is a bit too long by default. Th… by @wneessen in #78

Full Changelog: v0.3.3...v0.3.4

[BREAKING CHANGE] v0.3.3: MiddlewareType and WriteToSkipMiddleware

This release will break current Middleware implementations

For middlewares to be able to access the fully written mail message, we need a way to execute WriteTo without the calling middleware to be handled, otherwise we end up in an infinite loop.

This release introduces the MiddlewareType and the corresponding change of the Middleware interface. We now require to return the MiddlewareType when the Type() method on the interface is called. Conveniently MiddlewareType is an alias to a string.

This way we can also introduce the WriteToSkipMiddleware() method which takes a MiddlewareType as argument. This will allow us to use a WriteTo call with the initiating Middleware itself to be skipped.

Please note: This release will break any existing go-mail Middleware, since they don't provide a Type() method yet.

What's Changed

• Introducing MiddlewareType and WriteToSkipMiddleware by @wneessen in #70

Full Changelog: v0.3.2...v0.3.3

[BREAKING CHANGE] v0.3.2: New Reader type to satisfy io.Reader

Initially the Msg implemented a io.Reader interface by providing a Read methods. Unfortunately the method chosen for this method was very naive. It works fine for smaller messages but could result in wrong data returned for larger messages or i. e. used in a bufio.Reader with non consecutive reads. Since we did not track the position and state of the reading operation, duplicate data might be returned to the caller eventually even leading into infinite loops.

This release fixes the issue be introducing a new Reader type. The Reader type satisfies the io.Reader interface and returns the data properly as well as returns EOF in case the end of data is reached.

The initial Read() method has been removed from the Msg type and instead a NewReader() method has been introduced that returns the Reader type.

BREAKING CHANGE: Since we remove the Read method from the Msg the Msg does not satisfy the io.Reader interface anymore, which is considered a breaking change. But given that the returned data of the original implementation might return duplicate or wrong data, this breaking change is considered as the right decision.

What's Changed

• Introduce golangci-lint by @wneessen in #66
• Fix codecov Go version setup by @wneessen in #67
• New Reader type by @wneessen in #68

Full Changelog: v0.3.1...v0.3.2