Advanced Options LZMA


i installed Duplicati on my Windows PC just to test it a little and probably get used to it. Standard setting works great but when i try to set some advanced options it doesn´t work as plannend. For example i set in my Backup Options that i want to receive E-Mails and the compression Method should be LZMA. The files i get are still ZIP files and i can´t type anywhere to which E-Mail i want my messages. I guess this will work better on a Linux Server to set these options. But for the moment i just experiment a little on my Windows PC. Can somebody explain me why Duplicati ignoring my Options and how i set them right?

Best regards and thx for every help


don’t try LZMA, it don’t work.
To send emails, set the send-mail-to advanced option.

Making it work can be tricky, the best is to use the send-mail command (from the command line item in the Web UI). In this way you can see the mail server error directly.

Don’t forget to clear the unneeded parameters when switching from the default command (backup) to the send-mail command, especially the source path parameter.

No need to say that your answer made me laugh :smiley:
Thx for the answer, i´ll try.

Wish you a nice weekend.

Which option is being applied?

  --zip-compression-method (Enumeration): Sets the Zip compression method
    This option can be used to set an alternative compressor method, such as LZMA. Note that using another value than Deflate will cause the zip-compression-level option to be ignored.
    * values: None, Deflate, BZip2, LZMA, PPMd
    * default value: Deflate

seems to be working for me and

and that’s how it should be. You can look inside with the right tool, e.g. 7-Zip, to see compression:

Some people think that LZMA is slow, so pick the tradeoff. Also leave compression-module alone.
A .zip file is what you want, although I’m curious about what sort of non-ZIP file you had expected.

This also leaves me wondering what was set and what wasn’t. I tested an aspirational tiny setup:

  --send-mail-to (String): Email recipient(s)
    This setting is required if mail should be sent, all other settings have default values. You can supply multiple email addresses separated with commas, and you can use the normal address format as
    specified by RFC2822 section 3.4.
Example with 3 recipients:

Peter Sample <>, John Sample <>,

and it got past the GUI sanity check (maybe based on above help), then gave warning at run time

[Warning-Duplicati.Library.Modules.Builtin.ReportHelper-ReportSubmitError]: Failed to send message: System.ArgumentException: The host name cannot be empty. Parameter name: host

I expected need for mail server info, but there’s a feature (or misfeature?) that sometimes avoids it:

  --send-mail-url (String): SMTP Url
    A url for the SMTP server, e.g. smtp:// Multiple servers can be supplied in a prioritized list, separated with semicolon. If a server fails, the next server in the list is tried, until the
    message has been sent.
If no server is supplied, a DNS lookup is performed to find the first recipient's MX record, and all SMTP servers are tried in their priority order until the message is

To enable SMTP over SSL, use the format smtps:// To enable SMTP STARTTLS, use the format smtp:// or smtp:// If
    no port is specified, port 25 is used for non-ssl, and 465 for SSL connections. To force not to use STARTTLS use smtp://

Typically a public ISP will need send-mail-username and send-mail-password. Find your setup info.

these are the options i set. Maybe its more easy to set on a linux server, but as i said i tried on windows and i guess lacking of knowledge here. Thought there is a GUI where i can set my e-mail adress. At least an information where to set the e-mail adress.

I thought LZMA will supress 7 gb more than 6,5 gb as result, and have another ending than .zip. Chat GPT mentioned ending like .xz for LZMA.

Also would be interesting how to set up 7zip as compression method. I guess i need to choose compression-module but what do i need to type in?
i like the fact that i can choose a lot of advanced options but user manual don´t help me how to set up :confused:

It should be identical. From pick-an-option menu on Windows 10:


It’s right above, probably send-mail-to if you mean recipient, send-mail-from if you mean sender.
Reporting options in the manual describes them all, but so does the GUI after you pick some options.

I have no idea where the numbers came from, or even read that. 7 gb more than 6,5 gb gives 13,5 gb.
People who compare the two seem to think that LZMA often compresses better, but sometimes worse.
I already mentioned the speed concern that people have. Is your situation CPU-rich but space limited?
Basically, given the trouble you already have with options, why do you seek to wander down that path?

I shouldn’t have to advise this, but don’t believe everything Chat GPT says, especially in wrong context.

xz(1) - Linux man page
XZ Utils
XZ data compression in Linux

do, in Linux, tie .xz and LZMA2 (which is a successor to LZMA) together, but Deflate and LZMA are just compression algorithms that can be used anywhere, including in .zip files. Please read up, or drop this. You (or maybe Chat GPT) is mixing up compression algorithms with packaging file formats, and suffixing on various systems. If you read the Linux man page, you see that the utility just compresses a single file.

tar(1) - Linux man page is one way to work around that. It packages your files, then you compress its file, resulting in file suffixes such as .tar.gz or .tar.xz reminiscent of Duplicati’s .zip.aes that’s common.

Formats for SharpCompress (used by Duplicati for .zip files) shows archive and compression varieties.

Don’t use it. 7z doesn’t work. Stay on .zip


If you want to change .zip compression method, feel free but note that different .zip programs may support different methods, so you could introduce an incompatibility, but I did test Windows on LZMA. Most people don’t open Duplicati .zip files though, so it’s a minor worry but illustrates peril of choice.

Choosing a Compression Method is advice from WinZip, but implementations may also affect speeds.
RasterLite2 reference Benchmarks (2019 update) benchmarks some you can get and some you can’t.

Advanced options are by definition advanced. The GUI helps the setup, but choose at your own risk because some of them are probably very rarely used, so you could be the first to run into some issue. Some people might enjoy that, but if you just want things to work, stick close to defaults, as most do…

One notable exception is that on backups larger than 100 GB, scaling blocksize up helps performance.

First thx for the answer and help. Your post is helpful, to understand how some things work in duplicati and get a better understanding of compression.

With 7 GB and 6,5 GB i meant that i reduced the space from 7 to 6,5 with LZMA. I thought that would be clear in that circumstances (also my english was not the best there). Sorry if i didn´t get that clear enough.

At least there is no need to get mean. I try to find out how the Programm works and for me the best way is to ask people which are used to it to get an overview an see how things are working before i get deeper inside. Sometimes i ask also things not for the moment, but for future regards, just to get a better understanding. People have diffrent handlings in solving tasks and it would be awesome if a community helps without demotivating, is somebody get into new things, because the background knowledge in a specific topic is not state of the art. For me sometimes things are fine if they are working without knowing all stuff around.

So best regards and again thx.

It’s a good result, though small in absolute terms – maybe you’ll scale size up later but I don’t know.
If you plan to do a big backup, increase its blocksize now, as you won’t be able to increase it later.
Choosing sizes in Duplicati covers some other sizes, but doesn’t say much about blocksize scaling.

Email client (Wikipedia) can possibly provide some help if you’re still unclear on what you may need.
Submitting messages to a server is what you’re trying to do, so please consult with your provider for specific requirements they might have. One question in particular is how to get adequate security to protect your login credentials, and maybe the message contents (although it’s just a backup report).

Which SMTP port should I use? Understanding ports 25, 465 & 587 and other resources cover that.
Something of the format smtp:// might work for you.
Duplicati cannot know all email providers. Their requirements vary, so you may have to read or ask.

This is the path I was advocating. Eventually there’s lots more, but often no reason to rush ahead…

Getting things somewhat settled first is good, and as things get comfortable, maybe explore further, however jumping into deep technical areas such as LZMA might receive a very technical response.

I’m changing the category of post from Features to Support, as there’s no specific feature request.
Those get collected in one category so they can get discussed – but very few can actually get done.


thx for this line. From the explanation giving in Duplicati i would miss the smtp part after smtp:// and probably struggle. I get the E-Mail Notification working.

The smtp was made up, however some ISPs do use styles like that. Mine actually uses smtpauth

Again, Duplicati does not know what your ISP requires. You got lucky. If you didn’t then ask your ISP.