Custos is great because it 'just works'. I find with these new AI tools often they make big promises but when you go to actually use them...they suck (aka gemini's built in email writing tool). I've been looking for a simple, easy to use tool that makes getting to inbox 0 faster...and this is it. Custos understands my writing style and does a good job of historical context to draft emails that sound like me. I usually just have to add a few words and hit send...which is exactly what I am looking for. The 'adjust' feature where you can prompt it to change the email works well but I haven't gotten used to it yet. Definitely recommend this tool...I use it everyday.
Hi Product Hunt 👋
I’m Khalil, one of the founders of Custos.
We built Custos because we were spending way too much time writing emails that should have taken seconds. Drafting, rewording, overthinking all added up to hours lost every week.
Custos helps you reply faster by automatically drafting emails in two ways: it pre-generates responses the moment an email hits your inbox and it instantly writes replies when you hit respond. You don’t need to change how you work. Custos works directly from your Gmail inbox through a Chrome extension and API combination. Your emails stay natural, contextual, and sound just like you.
If you’re curious, we’d love for you to give it a try and share any feedback, questions, or ideas. People from companies like dLocal, Tabby, Puzzle, Antler and Web Summit are already using Custos and helping us make it better every day.
Visit our website and try Custos for free at https://www.withcustos.com/
@khalil_osman1 Hey! Congrats on going live, upvoted, we launched today as well and your feedback would help.
Visla
@khalil_osman1 great job Khalil! Good luck on the launch!
@mogabr Thank you!
@khalil_osman1 @omar_mostafa4 @joaquincoitino @hamahmi_custos I just downloaded but have yet to start playing around with the tool.. that being said.. I think its a great niche solution! Like @busmark_w_nika mentioned - leading with what the security parameters are might be helpful for some on the fence users (I'd assume).
A few questions (that may have already been answered)
1. Is there a way to train the software on my email style / speaking style / give it access to a knowledge base on how I WANT to speak (vs how I've spoken in the past)... ex if its trained on or has access to lots of my emails (many of which are internal) - I speak/write much differently to my colleagues than to customers / prospects etc.
1.a. If there is - would there be a way to toggle on specific (agents / knowledge bases / speaking styles) depending on the demo of who the email is being sent to?
2. What LLM is this trained on and can I choose one that I like best (presume I like the email outputs from claude more than GPT5) or I am a deepseek loyalist etc.
Either way - killer product and congrats on the launch - looking forward to seeing how things unfold for your team!
@omar_mostafa4 @joaquincoitino @hamahmi_custos @busmark_w_nika @dzaitzow Thanks Daniel! To answer your questions:
The emails leverage past context and we currently are focusing on making the setupas seamless as possible for now. With that being said, we are actively working on ways to be able to provide more context from documents and different types of knowledge bases to make everything more personalized. This is our core area of focus!
1a. Great point! We're completely aware that there are unique preferences for all users. As of now, we do not have this enabled, but again, it is something we are working on. There is a lot we can do around this considering we're built into the UI of gmail.
We use mostly OpenAI for our models (combination of GPT-4.1 and GPT-5) but personal model selection could be an interesting thing to eventually incorporate.
Thanks for the comment!
@omar_mostafa4 @joaquincoitino @hamahmi_custos @busmark_w_nika @khalil_osman1 Thanks for the insight! Looking forward to the updates and seeing how things unfold.
minimalist phone: creating folders
@khalil_osman1 @omar_mostafa4 @joaquincoitino @hamahmi_custos @dzaitzow This is a good point. I would also like to switch convo styles depending on who I write to.
@khalil_osman1 @omar_mostafa4 @hamahmi_custos @dzaitzow @busmark_w_nika so Custos automatically does that. It understands who you are speaking to and uses past emails to capture to how you speak in similar situations.
Ideal tool to save those micro-minutes when drafting emails. I’ve been using it and I like that it understands the previous conversation and the context for replying.
Question for the team… what data has been relevant for the team to make improvement decisions?
@juan_pablo_del_rio1 Thank you!
@juan_pablo_del_rio1 Thanks! We mainly do 3 things:
Calculate % of emails that we generate that get sent
Calculate "similarity" between the email we generate and the email that the user ends up sending
Most importantly, we speak to users continuously
Hello everyone,
Communication can be a very emotional and special thing. Repetitive and transactional comms is not. At Custos, we want to automate the latter so you have more time for the former.
We are starting with email. Our product works where you already work: Gmail. No new interfaces, menus or shortcuts to learn.
We built something not to only save others, but ourselves in the first place. We know how much of a pain it is, so we decided to ease it up on everyone.
Compassion and determination is put into every single detail.
Ahhh I love this, exactly the sort of tool that makes my life instantly 10x easier when I'm doing my daily work!
Thanks to the team for this & best of luck w/ the launch!
@cranqnow 🚀🚀
We've built this product to be as simple and intuitive to use as possible. If you've tried using Gemini in your Gmail and you never used it again, our product is for you!