I'm looking for a software sender for email letters.

Hello, I’m new to email newsletters, can you tell me everything I need to send at least 10k emails a day and not end up in spam? Tell me the best sender for letters, preferably with rotation

Try mail250

Mail250 or Woodpecker.co , these should help you. Woodpecker has a free trial I believe.

Atomic mail sender

For large volume, consider platforms like SendGrid or Mailgun. As for rotation, most ESPs offer IP rotation, crucial for deliverability.

You can try Mail250 and Atomic Mail Sender.

Mail 250 might be helpful.

Warning about atomic mail sender

I bought this software/key & after approximately 5 years,
for experiencing what anyone could experience with laptops, either
an end of life of: the fan, or the motherboard, or the videocard,
& replacing the second hand laptop with the same to avoid more
important repair costs, keeping the same hard drive & puting it
in another computer. The company sets a script that disables my
purchased key, after 3 changes, & pretends to help you by offering
you a 4th reactivation as if you were using a trial, & then a 5th,
& finally, they refused to confirm me they'd keep doing it in case
my hardware fails. & they also add that the software is bound to the
hardware making you loose the purchased key after 3 to 5 attempts.
So if you buy that software, tell yourself if you refuse to upgrade,
(endlessly "pay"), after buying new laptops or pcs, you will lose
your purchase. They pretend it's a violation of tos, as if these
russians don't understand that using several pcs with the software
is what's typically & normally a violation of tos & what i don't
actually do & they know it (confirmed by email). So change your pc
or laptop over time (which is a logical process) & you're loosing it
by a final deactivation.

Ps: i have their absurd response by emails with full mime headers
confirming you this situation.

If you want to send bulk mail at the lowest price, go with Mail250.