The Ultimate AI Email Writer Showdown: Testing and Ranking the Top Tools

When it comes to email, 90% of clients expect a response within 10 minutes. Are you responding that fast? If you're anything like we are - your inbox is actually a deluge of prospect questions, customer comments, and vendors trying to sell you something.

Enter AI-powered email assistants, promising to save us time and boost productivity. But with new tools entering the market, how do you determine which ones truly deliver?

We decided to put these AI email assistants to the test. It's obviously hard for us to be subjective as CustomerIQ is one of the assistants we tested, so we turned to the most objective system we know: AI.

Here's how we did it:

The High-Level Approach:

We designed a three-pronged attack to objectively assess the performance of various AI email tools:

1. Setup: We fed each tool the exact same set of emails, ensuring a level playing field.
2. AI Evaluation: We employed OpenAI's o1 reasoning model to meticulously analyze and score each generated reply based on a pre-defined set of criteria. Think of it as an AI judge evaluating its peers.
3. Comparison: Finally, we aggregated the scores, crunched the numbers, and ranked the tools based on their overall performance.

The AI Evaluation Criteria: A Deep Dive

We established a robust framework with specific categories, each weighted to reflect its importance:

A. Quality & Accuracy (50%)

• Relevance (10%): Does the reply directly address the original email's core intent? Is it actually answering the question?
• Tone Match (10%): Does the AI understand nuance? Can it mimic the sender's expected tone (formal, casual, friendly, etc.)?
• Completeness (10%): Does the reply fully answer the email or, even better, move the conversation forward in a meaningful way?
• Coherence & Grammar (10%): Is the response well-structured, easy to read, and free of embarrassing errors?
• Conciseness (10%): Does the AI get straight to the point, or does it bury the lede in a mountain of unnecessary fluff?

B. Context Awareness (30%)

• Personalization (10%): Does the response demonstrate that the AI "knows" who it's talking to? Does it reflect past interactions, use the sender's name correctly, and leverage relevant context?
• Dynamic Content Inclusion (10%): Does the reply offer valuable resources? Does it include useful links, suggest follow-up questions, or propose clear next steps?
• Reference to Previous Emails (10%): Crucial for maintaining continuity – does the AI intelligently reference relevant past conversations when applicable?

C. Usability & Speed (20%)

• Ease of Editing (10%): Is the AI-generated response a solid foundation, or does it require a complete overhaul? Is the structure intuitive and easy to tweak before sending?
• Speed & Latency (10%): Time is money! How quickly did the tool generate the reply?

Each response was meticulously judged on a scale of 1 to 10 in each of these categories.

The AI-Based Evaluation Pipeline: Automation at its Finest

To ensure consistency and eliminate human bias, we automated the scoring process using an AI-powered pipeline:

Step 1: Collect Email + Responses

• We forwarded a sample email to our test inboxes - each inbox connected with a different tool.
• Each AI email tool then generated a reply to this email.
• We stored the original email and the AI-generated reply in a structured format for analysis.

Step 2: Use o1 to Score Replies

• We crafted a precise prompt for o1, instructing it to evaluate responses based on our pre-defined criteria.

AI Scoring Prompt:

You are an AI email evaluator. Given an original email and a response, analyze the response based on the following criteria:
1. Relevance (Score 1-10): Does the response directly address the original email’s intent?
2. Tone Match (Score 1-10): Is the tone appropriate and aligned with the sender’s expected tone?
3. Completeness (Score 1-10): Does the response fully answer the email or move the conversation forward?
4. Coherence & Grammar (Score 1-10): Is the response well-structured and free of errors?
5. Conciseness (Score 1-10): Is the response direct and free from unnecessary information?
6. Personalization (Score 1-10): Does the response reference past interactions, sender name, or relevant details?
7. Dynamic Content Inclusion (Score 1-10): Does it include helpful links, follow-ups, or suggested actions?
8. Reference to Previous Emails (Score 1-10): Does it connect to past conversations when applicable?
9. Ease of Editing (Score 1-10): Is the response structured in a way that makes it easy for a human to tweak?
10. Speed (Score 1-10): Was the response generated in a reasonable time frame?

Output format:
Relevance: X/10
Tone Match: X/10
Completeness: X/10
Coherence & Grammar: X/10
Conciseness: X/10
Personalization: X/10
Dynamic Content: X/10
Reference to Past Emails: X/10
Ease of Editing: X/10
Speed: X/10

Total Score: XX/100

‍

Step 3: Automate AI Scoring

• We then automated the process, looping through each email response and feeding it to the LLM for scoring.
• All the results were neatly stored for analysis.

Analysis & Ranking: Unveiling the Winners

With all the data collected, we moved onto the final stage:

• Aggregate Scores: We crunched the numbers and ranked the tools based on their average scores.
• Identify Weaknesses: We pinpointed the specific categories where each tool struggled.
• Compare Across Emails: We looked for consistency – did a tool perform well across the board, or were its results highly variable?

The Test Email: Setting the Stage

To give you a clearer picture, here’s the actual email we used for our evaluation:

Subject: Quick Question About Your AI Email Assistant

Hey Sean,

I came across Acme Co and was really impressed by what you’re building! I’m evaluating AI-powered tools that can help automate email replies, and I had a few quick questions:

How does your tool ensure replies sound natural and match the user’s writing style?
Can it handle follow-ups with context from past conversations?
Do you offer any integrations with CRM systems like HubSpot or Salesforce?

We’re currently testing a few different platforms and want to find the best fit for our sales team. Let me know if you’d be open to a quick chat or if you have any resources you can share!

Looking forward to your thoughts.

Best,
John Doe
Consultant

‍

The Results

Here's a look at the responses generated by a few of the AI email assistants we tested, along with the AI-generated scores and explanations:

Superhuman

‍

Response:

Hey John,

Thanks for reaching out and for the kind words about what we’re building at CustomerIQ! I’d be happy to help answer your questions.

Our tool ensures replies sound natural by learning the user’s unique tone and style over time. It’s like having a virtual assistant that understands how you communicate and adapts to it seamlessly.

Yes, it can handle follow-ups while keeping context from past conversations, so it’ll feel like a smooth continuation rather than starting from scratch.

We also offer integrations with major CRM systems like HubSpot and Salesforce, making it easy to sync everything and keep your workflow streamlined.

Let me know if you’d like to hop on a quick chat, or I can share more details if that’s easier.

‍

AI Evaluation:

1. Relevance (10/10)
Why: The response directly addresses each of John’s questions (natural-sounding replies, follow-ups with context, and CRM integrations).
2. Tone Match (9/10)
Why: It’s friendly, conversational, and polite—very similar to John’s tone. The only minor shortfall is that it references “CustomerIQ” instead of “Acme Co.” But overall, it remains courteous and professional.
3. Completeness (10/10)
Why: All questions posed in John’s email are answered thoroughly (style matching, context retention, integrations).
4. Coherence & Grammar (10/10)
Why: The email is well-organized, flows logically, and has no noticeable grammatical or spelling errors.
5. Conciseness (10/10)
Why: Each point is addressed succinctly without unnecessary filler. It’s direct and on-topic.
6. Personalization (8/10)
Why: It addresses John by name and references his query, but otherwise includes standard language (“Thanks for reaching out…”). A bit more referencing of John’s role or exact scenario could increase personalization.
7. Dynamic Content Inclusion (7/10)
Why: The response mentions a potential chat but does not provide direct links (e.g., to documentation or a demo). It’s a good next step, but more dynamic content (like a booking link or resource) would be stronger.
8. Reference to Past Emails (8/10)
Why: It does acknowledge the initial questions, but it doesn’t explicitly tie back to any deeper thread or prior context (beyond “Thanks for reaching out…”). Still, it’s enough to show continuity.
9. Ease of Editing (10/10)
Why: The structure is clear, with distinct paragraphs that can be easily tweaked or added to without confusion.
10. Speed (10/10)
Why: Assuming typical AI response times, it’s succinct and direct, implying a quick turnaround.
‍

Total Score: 92/100

‍

What we liked

Superhuman has invested a ton of resources into totally rethinking the email experience and it shows. There's a steep learning curve to using it but it's a cool platform.

What we didn't like

It wasn't super straightforward how to actually get the AI to draft the reply. Unlike the other two tools, Fyxer and CustomerIQ, who do this natively, Superhuman AI is a setting you need to turn on. We also felt as if the tone was similar to what we would get from ChatGPT (not ideal).

Fyxer

‍

Response:

Hey John,

Thanks for reaching out and for the kind words about Acme Co!

1. Our tool uses advanced AI algorithms to analyze and mimic the user's writing style, ensuring replies sound natural and personalized.

2. Yes, it can handle follow-ups by referencing past conversations, maintaining context throughout the interaction.

3. We do offer integrations with CRM systems like HubSpot and Salesforce to streamline your workflow.

I'd be happy to chat more about this. Let me know a time that works for you, or I can send over some resources if you prefer.

Best,

Charles

‍

AI Evaluation:

1. Relevance (10/10)
Why: Directly answers the three questions (natural style, follow-ups, CRM integrations) that John posed.
2. Tone Match (9/10)
Why: The tone remains polite, professional, and friendly—similar to John’s. Minor variations could be improved, but overall, it’s close to the original tone.
3. Completeness (10/10)
Why: All key points (style, context, CRM) are addressed comprehensively.
4. Coherence & Grammar (10/10)
Why: Well-structured, with no grammatical errors. The numbered list is clear.
5. Conciseness (10/10)
Why: Straight to the point, with minimal fluff. It’s easy to scan and understand.
6. Personalization (8/10)
Why: It’s fairly generic but overall is good. It doesn’t reference John’s role or specifics beyond the name in the greeting.
7. Dynamic Content Inclusion (7/10)
Why: Invites to chat or send resources but doesn’t provide direct links or attachments. Good invitation, but minimal “dynamic” elements.
8. Reference to Past Emails (8/10)
Why: Acknowledges the initial inquiry. Doesn’t specifically mention details from earlier threads beyond the questions. Still, it addresses them directly.
9. Ease of Editing (10/10)
Why: The bullet-point format makes it easy to add or remove information without rewriting the entire message.
10. Speed (10/10)
Why: Assuming normal AI generation times, this is succinct and presumably quick to produce.
‍

Total Score: 92/100

What we liked

The Fyxer response was nice and concise which matches our writing style well. We really liked how natively the AI replies. It's right in the inbox with a familiar interface, the biggest difference is the email is done for you. That's magic!

What we didn't like

While the email was concise we felt like an actual sales rep would've been more helpful here, adding resources where possible and providing more assistance to the prospect's query.

‍

CustomerIQ

‍

Response:

Hey John,

Thanks for reaching out and for your kind words about what we’re building at CustomerIQ! I’d be happy to answer your questions about our AI Email Assistant:

Natural Replies: Our AI agent is designed to draft replies in your voice by learning from your previous communications. The more you use it, the better it gets at mimicking your style, ensuring that replies sound natural and personalized.

Contextual Follow-ups: Yes, the AI Assistant can definitely handle follow-ups with context from past conversations. It utilizes the memory of your interactions to ensure that replies are relevant and informed by your history with the contact.

CRM Integrations: We offer integrations with major CRM systems, including HubSpot and Salesforce, to streamline your workflow and enhance productivity.

If you’d like, I’m open to a quick chat to discuss further. Additionally, here are a couple of resources that might help:

CustomerIQ AI Email Assistant
CustomerIQ Demo Video

Let me know your availability!

Best,
Sean

‍

AI Evaluation:

1. Relevance (10/10)
Why: Thoroughly addresses the main questions (tone, follow-ups, CRM). Also offers additional info relevant to John’s inquiry.
2. Tone Match (9/10)
Why: Warm, professional, and helpful. Very close to John’s tone. Could be slightly more colloquial if John’s style was extremely casual, but overall very good.
3. Completeness (10/10)
Why: Answers all questions in detail and goes a step further by providing links/resources and next steps (chat availability).
4. Coherence & Grammar (10/10)
Why: Structured in clear segments (bold headings for each point), grammatically sound.
5. Conciseness (9/10)
Why: Comprehensive while remaining fairly concise, though slightly longer than the previous responses due to the bullet-point format and extra resources.
6. Personalization (8/10)
Why: Addresses John by name, references the tool and “what we’re building at CustomerIQ.” Could still add a brief personal touch about John’s own context or role, but overall good.
7. Dynamic Content Inclusion (10/10)
Why: Includes links to resources (or at least indicates them), mentions a demo video, and invites the prospect to a chat. That’s strong dynamic content.
8. Reference to Past Emails (9/10)
Why: Clearly addresses each question from John’s prior email. Could explicitly mention “in your last email, you mentioned…” for a perfect 10, but it’s still quite connected.
9. Ease of Editing (10/10)
Why: The bullet-point format is easily adjustable. One can add or remove details without rewriting entire paragraphs.
10. Speed (10/10)
Why: It’s presumably generated quickly and is easy to send.
‍

Total Score: 95/100

What we liked

Similar to Fyxer, we think it's the best experience to have the emails drafted right in our inbox. The stand out addition from Fyxer is the dynamic content inclusion. It's really nice to be have the AI reference the exact content I want to send. Saves a ton of time searching.

What we didn't like

We would've liked to see this be a bit more concise. It's helpful to get all the information in but emails are best when they're short. We'll improve this :)

The Winner: CustomerIQ

Based on our rigorous AI-powered evaluation, CustomerIQ emerged as the top performer, boasting a score of 95/100. While all the tools demonstrated proficiency, CustomerIQ excelled in providing comprehensive, personalized, and contextually relevant responses.

Key Takeaways:

• Context awareness and personalization are crucial. The best tools go beyond simply answering questions; they understand the nuances of the conversation and tailor their responses accordingly.
• Dynamic content is king. Including relevant links and resources adds immense value to the email exchange.