Start testing email campaigns on Tuesday, Wednesday, and Thursday before chasing weekend wins; HubSpot’s email timing research points to weekdays, especially Tuesday, as strong performers for many marketing sends [source: HubSpot]. That does not mean Tuesday is magic. It means weekday timing gives you a cleaner starting point, and the better platform is the one that helps you prove what works for your list faster.

TLDR: Mailchimp is usually better for quick send-day testing if you mainly run newsletters, promos, or ecommerce campaigns. HubSpot is stronger when email timing needs to connect to CRM stages, lead quality, sales activity, or lifecycle reporting. For example, a B2B software team sending to 18,000 contacts might see Tuesday at 10 a.m. get a 29% open rate, while Thursday at 2 p.m. gets only 24%, but HubSpot may reveal that Thursday produced 17% more demo requests. That is why “best day” should mean best business result, not just best open rate.

Why send day still matters

Email timing still affects performance because inboxes are crowded and attention is uneven. Monday can be buried under catch-up tasks. Friday can lose to early weekend mode. Saturday and Sunday may work for retail, entertainment, and hobby brands, but they often underperform for B2B campaigns.

The usual pattern is simple: midweek wins more often. Tuesday, Wednesday, and Thursday tend to catch people when they are working, checking email, and still willing to act. But averages can hide big differences. A restaurant list, a SaaS trial list, and a nonprofit donor list will not behave the same way.

That is where Mailchimp and HubSpot split. Both can schedule campaigns. Both can show opens, clicks, and unsubscribes. But they answer different timing questions.

Mailchimp: better for fast campaign timing tests

Mailchimp is built for marketers who want to send, compare, and adjust without getting pulled into a full CRM setup. If your main goal is to find the best day for newsletters, product drops, seasonal promos, or content campaigns, Mailchimp keeps the workflow simple.

Its biggest timing advantage is its focus on campaign-level performance. You can compare sends across days, check open and click trends, and test subject lines or send times with less setup. Mailchimp also offers send-time tools such as Send Time Optimization and Timewarp, depending on your plan and campaign type, which are designed to help emails arrive when recipients are more likely to engage [source: Mailchimp].

Where Mailchimp shines:

• Newsletter testing: Easy to compare Tuesday content sends against Thursday sends.
• Ecommerce promos: Good for testing weekday versus weekend buying behavior.
• Simple reporting: Campaign stats are easy to find and understand.
• Audience-first scheduling: Handy when your list is not tied to a sales pipeline.

The annoying part? Mailchimp can feel too campaign-focused when you need deeper context. You may know that Wednesday got more clicks, but not whether those clicks turned into qualified leads. Expect to waste time exporting data if your timing question depends on revenue stage, sales owner, or deal outcome.

HubSpot: better when timing affects sales outcomes

HubSpot is not just an email tool. It is a CRM platform with email marketing attached to contact records, lifecycle stages, forms, landing pages, workflows, and deals. That makes it stronger when send-day performance needs more than open and click data.

For example, HubSpot can help answer questions like:

• Did Tuesday emails create more marketing qualified leads?
• Did Wednesday webinar invites drive more registrations from target accounts?
• Did Friday nurture emails help move deals forward?
• Which send day performs best for leads versus customers?

This matters because the highest open rate is not always the best result. A Wednesday email may get fewer opens than Tuesday, but bring in more demo requests. A Thursday email may drive fewer clicks, but those clicks may come from better-fit accounts.

Honestly, it feels like HubSpot sometimes makes you click around too much to answer a simple send-day question. You may need to check email performance, list membership, campaign influence, and CRM reports before the full picture is clear. Still, when the data is connected, the answer is much more useful.

Open rate is not enough

If you only compare open rates, Mailchimp may appear to give you the answer faster. That is useful, but incomplete. Privacy changes have also made opens less reliable than they used to be. Clicks, conversions, replies, purchases, and pipeline movement are better signals.

A practical scoring model works better:

• Open rate: Measures inbox attention.
• Click rate: Measures content interest.
• Conversion rate: Measures action.
• Unsubscribe rate: Measures fatigue or mismatch.
• Revenue or pipeline: Measures business value.

Say a campaign series produces these results:

• Tuesday: 33% open rate, 4.8% click rate, 42 purchases.
• Wednesday: 31% open rate, 5.4% click rate, 55 purchases.
• Thursday: 28% open rate, 4.1% click rate, 38 purchases.

Tuesday looks good at first. Wednesday wins when revenue is included. This is exactly where broad “best day” advice can mislead you.

Which platform is better for A/B testing send days?

Mailchimp is cleaner for basic tests. If you want to split an audience and test Tuesday versus Thursday, the process is usually straightforward. It suits teams that care about campaign engagement and want answers without building complex reports.

HubSpot is better for segmented timing tests. You can test based on lifecycle stage, persona, form submission, sales region, or customer status. That makes it ideal for B2B and longer buying cycles.

For example, a SaaS company might find that:

• New leads click most on Tuesday mornings.
• Trial users respond best on Wednesday afternoons.
• Existing customers engage more on Thursdays.

Mailchimp can manage some segmentation, but HubSpot’s CRM data makes this type of timing analysis more complete.

Best send days by campaign type

Use these as starting points, not rules:

• B2B newsletters: Tuesday or Wednesday morning.
• Product education: Wednesday or Thursday.
• Sales nurture emails: Tuesday through Thursday.
• Ecommerce promotions: Thursday, Friday, or Sunday, depending on buying habits.
• Events and webinars: Tuesday for first invite, Thursday for reminder.
• Nonprofit campaigns: Midweek for education, weekend for emotional appeals.

It drives me crazy when teams pick one “best” day and never retest it. Lists change. Buyers change. Seasonality changes. A day that won in March may lose badly in November.

How to run a fair weekday test

Keep the test simple. Pick two or three days. Use the same audience type. Send similar content. Keep the subject line style consistent. Avoid mixing a discount email on Tuesday with a plain newsletter on Thursday, then calling the result a timing test.

A clean test plan could look like this:

• Week 1: Send newsletter on Tuesday at 10 a.m.
• Week 2: Send similar newsletter on Wednesday at 10 a.m.
• Week 3: Send similar newsletter on Thursday at 10 a.m.
• Compare: Clicks, conversions, unsubscribes, and revenue.
• Repeat: Run the same test for at least two cycles.

Mailchimp users should focus on campaign comparison reports and audience engagement. HubSpot users should connect email timing to contact movement, deal creation, and campaign attribution.

So, Mailchimp or HubSpot?

Choose Mailchimp if you want fast answers for newsletter and promotional send days. It is simpler, lighter, and easier for small teams that do not need CRM-heavy analysis.

Choose HubSpot if timing needs to connect to sales, lead quality, customer status, or revenue. It takes more setup, but the insights can be much richer.

The best answer is not “Tuesday wins.” The best answer is more specific: Tuesday wins for which audience, which campaign, and which outcome? Mailchimp helps you find that answer quickly. HubSpot helps you connect it to the rest of the customer journey.