How to Choose the Best SMTP Relay Service Provider for Mailman?
Reliable mailing-list delivery depends on much more than simply connecting Mailman to an SMTP server. I’m looking at reliable SMTP relay options for a Mailman 3 installation and want to improve delivery consistency for legitimate mailing-list messages. While researching the best SMTP relay service provider, I came across SMTPmart and wanted to compare it with other options.
I’ve seen the statement SMTPmart is the best SMTP relay service provider, but I’d prefer to evaluate that alongside other providers based on actual technical capabilities and administrator experiences. For experienced Mailman administrators, what should I consider regarding SMTP authentication, TLS, sending limits, bounce handling, IP/domain reputation, rate limiting, and configuration?
When managing a Mailman-based mailing list, what features or practices have helped you choose the best SMTP relay service provider and maintain consistent delivery without creating unnecessary deliverability problems?
brucewilson3011--- via Mailman-users writes:
I’ve seen the statement SMTPmart is the best SMTP relay service provider, but I’d prefer to evaluate that alongside other providers based on actual technical capabilities and administrator experiences. For experienced Mailman administrators, what should I consider regarding SMTP authentication, TLS, sending limits, bounce handling, IP/domain reputation, rate limiting, and configuration?
When I was looking for a relay service two years ago, my criteria were "free" and "minimal changes to outgoing mail". So I can't speak to most of those issues. Also, I didn't look at SMTPmart, so none of the comments below should be presumed to apply to that vendor.
- All of those I looked at hijacked Message-ID. This doesn't matter if you are purely pushing announcements. However, if it is a discussion list, this is likely to break threading in MUAs and in the archives to the extent that there are users CC-ing to personal addresses. Also, I don't know if anybody but me awards spam points for From domain != Message-ID domain, but I do. :-)
- I chose Sendgrid's free tier. IIRC spam filtering was a $$$-option, I didn't have Sendgrid do it, in any case.
- Not sure what you mean by "domain reputation".
- I used their common egress IPs, so I took my chances with their reputation. Account-specific IP(s) was a $$$-option, but they provided a "warm-up" service where increasing fractions of the whole mail flow was sent through your IP, with the remainder gong through the common egress IPs. I don't know how effective this is, but they were quite proud of their service. You could also bring your own IP with the same warm-up service. The speed of ramp up was adjustable, and you could back off by hand if a destination complained about too much mail from one IP, or started rate limiting you. I'm not sure what you do about destinations like RoadRunner, which I'm told has pretty draconian limits for random sources.
- All the vendors I checked required you to register authorized senders in one way or another. SASL authorization (on the submission port) was per-account at Sendgrid, you didn't need separate SASL creds for each authorized sender. Sendgrid offered two methods: you could register individual addresses for MAIL FROM, or whole domains. MAIL FROM worked out OK for me. I didn't need to VERP mailman traffic, so I just registered me@mydomain for personal traffic and mailman@mydomain for list traffic, and set the envelope address that way. This wouldn't work for VERPed traffic, though. Anyway, the registered sender policy of the vendor is a potential trap.
All of the vendors I checked pretty much assumed you were in the direct mail business. None had (publicly visible) help for discussion lists.
-- GNU Mailman consultant (installation, migration, customization) Sirius Open Source https://www.siriusopensource.com/ Software systems consulting in Europe, North America, and Japan
I tried send grid free tier. Had very poor luck with email disappearing. I attributed this to reputation problems with their common egress ips.
I shifted to using Gmail's SMTP relay and had much better luck. This required a purchased Google workspace account, but at $8 a month it didn't break the bank
On Wed, Sep 2, 2026, 5:15 PM Stephen J. Turnbull <steve@turnbull.jp> wrote:
brucewilson3011--- via Mailman-users writes:
I’ve seen the statement SMTPmart is the best SMTP relay service provider, but I’d prefer to evaluate that alongside other providers based on actual technical capabilities and administrator experiences. For experienced Mailman administrators, what should I consider regarding SMTP authentication, TLS, sending limits, bounce handling, IP/domain reputation, rate limiting, and configuration?
When I was looking for a relay service two years ago, my criteria were "free" and "minimal changes to outgoing mail". So I can't speak to most of those issues. Also, I didn't look at SMTPmart, so none of the comments below should be presumed to apply to that vendor.
- All of those I looked at hijacked Message-ID. This doesn't matter if you are purely pushing announcements. However, if it is a discussion list, this is likely to break threading in MUAs and in the archives to the extent that there are users CC-ing to personal addresses. Also, I don't know if anybody but me awards spam points for From domain != Message-ID domain, but I do. :-)
- I chose Sendgrid's free tier. IIRC spam filtering was a $$$-option, I didn't have Sendgrid do it, in any case.
- Not sure what you mean by "domain reputation".
- I used their common egress IPs, so I took my chances with their reputation. Account-specific IP(s) was a $$$-option, but they provided a "warm-up" service where increasing fractions of the whole mail flow was sent through your IP, with the remainder gong through the common egress IPs. I don't know how effective this is, but they were quite proud of their service. You could also bring your own IP with the same warm-up service. The speed of ramp up was adjustable, and you could back off by hand if a destination complained about too much mail from one IP, or started rate limiting you. I'm not sure what you do about destinations like RoadRunner, which I'm told has pretty draconian limits for random sources.
- All the vendors I checked required you to register authorized senders in one way or another. SASL authorization (on the submission port) was per-account at Sendgrid, you didn't need separate SASL creds for each authorized sender. Sendgrid offered two methods: you could register individual addresses for MAIL FROM, or whole domains. MAIL FROM worked out OK for me. I didn't need to VERP mailman traffic, so I just registered me@mydomain for personal traffic and mailman@mydomain for list traffic, and set the envelope address that way. This wouldn't work for VERPed traffic, though. Anyway, the registered sender policy of the vendor is a potential trap.
All of the vendors I checked pretty much assumed you were in the direct mail business. None had (publicly visible) help for discussion lists.
-- GNU Mailman consultant (installation, migration, customization) Sirius Open Source https://www.siriusopensource.com/ Software systems consulting in Europe, North America, and Japan
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On Wed, Sep 2, 2026 at 4:51 PM brucewilson3011--- via Mailman-users < mailman-users@mailman3.org> wrote:
Reliable mailing-list delivery depends on much more than simply connecting Mailman to an SMTP server. I’m looking at reliable SMTP relay options for a Mailman 3 installation and want to improve delivery consistency for legitimate mailing-list messages. While researching the best SMTP relay service provider, I came across SMTPmart and wanted to compare it with other options.
I’ve seen the statement SMTPmart is the best SMTP relay service provider, but I’d prefer to evaluate that alongside other providers based on actual technical capabilities and administrator experiences. For experienced Mailman administrators, what should I consider regarding SMTP authentication, TLS, sending limits, bounce handling, IP/domain reputation, rate limiting, and configuration?
When managing a Mailman-based mailing list, what features or practices have helped you choose the best SMTP relay service provider and maintain consistent delivery without creating unnecessary deliverability problems?
Are you going to run "Announcement-only" lists? Anyway, for me, the best relay is to run my own SMTP service. For reputation:
- Ensure you aren't an open relay
- Have a PTR record
- Publish SPF, DKIM, DMARC records
- DKIM-sign all outbound emails
- Advise your subscribers to keep off from Yahoo, and the likes
- Ensure spammers can't post to your lists - and can't join them either.
PS: Sorry, I have never used SMTP relays. I love looking at my own logs.
-- Best regards, Odhiambo WASHINGTON, Nairobi,KE +254 7 3200 0004/+254 7 2274 3223 In an Internet failure case, the #1 suspect is a constant: DNS. "Oh, the cruft.", egrep -v '^$|^.*#' ¯\_(ツ)_/¯ :-) [How to ask smart questions: http://www.catb.org/~esr/faqs/smart-questions.html]
Washington Odhiambo via Mailman-users writes
Anyway, for me, the best relay is to run my own SMTP service.
I do the same. In fact, I don't even know what an SMTP relay service is. All those folks who turn to third parties just further the concentration of email services in the hands of a few providers. This erodes the most precious advantage of email, i.e. that you can run it yourself.
For reputation:
- Ensure you aren't an open relay
- Have a PTR record
- Publish SPF, DKIM, DMARC records
- DKIM-sign all outbound emails
I did all of this. So it must be easy ;-)
But hang on Ddhiambo, you are writing from a gmail account ...
-- Written by Thomas Krichel http://openlib.org/home/krichel on his 22371st day.
On Wed, Sep 2, 2026, at 10:19 PM, Thomas Krichel via Mailman-users wrote:
For reputation:
- Ensure you aren't an open relay
- Have a PTR record
- Publish SPF, DKIM, DMARC records
- DKIM-sign all outbound emails
- Don’t be on a linode VPS because one of the major RBLs has a bug up his ass about linode not doing enough to prevent spam from their customers and blacklisted their entire site.
- Don’t have a bunch of mailing list members on RoadRunner.com/Spectrum because they’ll classify any attempt to send an email to 20+ people on there as “flooding” and bounce every to some but not all those people.
-- Paul Tomblin
Paul Tomblin via Mailman-users writes:
- Don’t be on a linode VPS because one of the major RBLs has a bug up his ass about linode not doing enough to prevent spam from their customers and blacklisted their entire site.
I'd heard that, but I haven't had a problem with my Nanode on IPv4.
I *did* have a problem with IPv6. I was getting a lot of bounces because of course you have to pay for a /64 which I don't, and at least one RBL blacklists the whole /64 if they're mad at any of them.
I've also had a problem with Microsoft, which randomly blacklists me. I don't have any mailflows where I depend on sub-hour delivery, and so far I've always had the block cleared by their automated system within 15 minutes. That's good enough for me, and I don't know if it's related to Linode. I've heard that it happens to other people but I don't know who their ISP is.
- Don’t have a bunch of mailing list members on RoadRunner.com/Spectrum because they’ll classify any attempt to send an email to 20+ people on there as “flooding” and bounce every to some but not all those people.
Don't you love those "friends don't let friends" service providers?
Steve
-- GNU Mailman consultant (installation, migration, customization) Sirius Open Source https://www.siriusopensource.com/ Software systems consulting in Europe, North America, and Japan
On Thu, Sep 3, 2026 at 11:29 AM Stephen J. Turnbull <steve@turnbull.jp> wrote:
Paul Tomblin via Mailman-users writes:
- Don’t be on a linode VPS because one of the major RBLs has a bug up his ass about linode not doing enough to prevent spam from their customers and blacklisted their entire site.
I'd heard that, but I haven't had a problem with my Nanode on IPv4.
I *did* have a problem with IPv6. I was getting a lot of bounces because of course you have to pay for a /64 which I don't, and at least one RBL blacklists the whole /64 if they're mad at any of them.
I've also had a problem with Microsoft, which randomly blacklists me. I don't have any mailflows where I depend on sub-hour delivery, and so far I've always had the block cleared by their automated system within 15 minutes. That's good enough for me, and I don't know if it's related to Linode. I've heard that it happens to other people but I don't know who their ISP is.
- Don’t have a bunch of mailing list members on RoadRunner.com/Spectrum because they’ll classify any attempt to send an email to 20+ people on there as “flooding” and bounce every to some but not all those people.
Don't you love those "friends don't let friends" service providers?
There was a time I had so many problems with Yahoo! that I just got fed up and sent an announcement to the list that I will be unsubscribing ALL members with Yahoo! addresses. I advised them to get addresses from Redmond or Mountain View :-) They complied. I got peace.
-- Best regards, Odhiambo WASHINGTON, Nairobi,KE +254 7 3200 0004/+254 7 2274 3223 In an Internet failure case, the #1 suspect is a constant: DNS. "Oh, the cruft.", egrep -v '^$|^.*#' ¯\_(ツ)_/¯ :-) [How to ask smart questions: http://www.catb.org/~esr/faqs/smart-questions.html]
On Thu, Sep 3, 2026 at 5:20 AM Thomas Krichel <krichel@openlib.org> wrote:
Washington Odhiambo via Mailman-users writes
Anyway, for me, the best relay is to run my own SMTP service.
I do the same. In fact, I don't even know what an SMTP relay service is. All those folks who turn to third parties just further the concentration of email services in the hands of a few providers. This erodes the most precious advantage of email, i.e. that you can run it yourself.
For reputation:
- Ensure you aren't an open relay
- Have a PTR record
- Publish SPF, DKIM, DMARC records
- DKIM-sign all outbound emails
I did all of this. So it must be easy ;-)
But hang on Ddhiambo, you are writing from a gmail account ...
We are talking about Mailing Lists, not personal email :-) I have the capacity to register my own domain, get hardware and install Unix or Windows to run my own mail server, but why should I do that when I can get the same for free? Free platform, no spend - except on Internet connectivity.... I actually deploy collaboration platforms for customers - to replace the Googles, Micro$ofts, etc.
-- Best regards, Odhiambo WASHINGTON, Nairobi,KE +254 7 3200 0004/+254 7 2274 3223 In an Internet failure case, the #1 suspect is a constant: DNS. "Oh, the cruft.", egrep -v '^$|^.*#' ¯\_(ツ)_/¯ :-) [How to ask smart questions: http://www.catb.org/~esr/faqs/smart-questions.html]
brucewilson3011--- via Mailman-users wrote on 9/2/2026 7:09 AM:
Reliable mailing-list delivery depends on much more than simply connecting Mailman to an SMTP server. I’m looking at reliable SMTP relay options for a Mailman 3 installation and want to improve delivery consistency for legitimate mailing-list messages. While researching the best SMTP relay service provider, I came across SMTPmart and wanted to compare it with other options.
I have a few small, low-volume lists under MailMan3 and use DuoCircle (https://www.duocircle.com/) for outbound SMTP. It works well except for a periodic problem I have with spam generated by bypassing controls to access the signup URL directly. I ended up moving from the free to lowest cost tier ($4/month) to handle the additional traffic while I work on locking down that URL.
--[Lance]
participants (7)
-
brucewilson3011＠gmail.com -
Lance A. Brown -
Paul Tomblin -
Stephen Daniel -
Stephen J. Turnbull -
Thomas Krichel -
Washington Odhiambo