What is the best alternative to Spark Mail: AI Email Assistant on iPhone?

Superhuman Mail, S tier, #2 in email writing.

Is there a free alternative to Spark Mail: AI Email Assistant?

Yes: Superhuman Mail (S tier, #2) is free, with no in-app purchases.

No. Spark Mail: AI Email Assistant is #1 in email writing.

Spark Mail: AI Email Assistant is S tier, #1 of 6 in email writing. Here is everything that competes with it on iPhone, in tier order.

2
Superhuman MailS
Free · ★ 4.6 · 3,711 ratings · score 90
Email app for Gmail and Outlook with AI draft replies, inbox splits, automatic reminders, and HubSpot and Salesforce.
3
Canary Mail - AI EmailA
Free download · ★ 4.5 · 8,791 ratings · score 89
Email app that puts Gmail, Outlook, iCloud and other accounts into one inbox, with AI writing help, sorting, scheduling.
4
Friday AI Email WriterA
Free download · ★ 4.8 · 9,785 ratings · score 89
AI assistant that drafts emails and letters, proofreads text, and suggests writing edits from typed or voice input.
5
AI Writer: Email Letter EssayA
Free download · ★ 4.8 · 6,637 ratings · score 87
Free iOS app listed as Reference that generates writing for emails, letters and essays using AI, with voice dictation.
6
ParagraphAI: Writer & KeyboardB
Free + IAP · ★ 4.8 · 2,523 ratings · score 79
Free AI writing assistant and AI keyboard for drafting, editing, summarizing and translating text in 40+ languages.

What is the best alternative to Spark Mail: AI Email Assistant on iPhone?: Superhuman Mail, S tier, #2 in email writing.
Is there a free alternative to Spark Mail: AI Email Assistant?: Yes: Superhuman Mail (S tier, #2) is free, with no in-app purchases.
Does anything rank above Spark Mail: AI Email Assistant?: No. Spark Mail: AI Email Assistant is #1 in email writing.